Why don't Cantonese speakers write their own language? For me the most difficult thing about learning Cantonese has been that there are very few learning materials for foreigners (and I assume even for Chinese people). And even the materials that exist are all only regarding basic conversational topics. There is basically no Cantonese literature at all.
When I learned French it was very helpful to be able to follow audiobooks of stories from writers like Voltaire. The closest thing is watching Hong Kong movies, but they speak quickly and the subtitles are in Mandarin not Cantonese.

Are there any Cantonese literature or audiobooks out there?

A question for those Cantonese of you out there: Why does it seem that Cantonese people are so unwilling the write their own language? I understand that if you write Cantonese then other Chinese will not be able to understand, but so what? That sounds like their problem.

For the Vietnamese we used to write everything in Classical Chinese (文言). Since then we've switched to writing in our own language. We like it and are not ashamed of it. I don't see why the Cantonese shouldn't do similarly.

I don't understand why Cantonese are fiercely defensive of their language and at the same time refuse to write it down.
Why not write in written Cantonese?

Cantonese speakers are not unwilling to write their own language. Nowadays, written Cantonese is often used in lyrics, instant messaging, social network, advertisements and billboards. It is also gaining public attention as the Government of China wants to ban it. 

There is a Yue Wikipedia site containing 40,000+ articles written in Cantonese. However, written Cantonese is almost always used only in informal writings.

For formal writings, standard written Chinese is being used. It is taught in school to write in standard written Chinese (i.e. written Mandarin). It is because Mandarin was chosen as the basis for standard written Chinese as they had the largest number of speakers during the language reform. 


  No matter which dialect one spoke, one still wrote in standardised Mandarin for everyday writing. However, Cantonese is unique amongst the non-Mandarin varieties in having a widely used written form. (Wikipedia)


Standard written Chinese is understood by speakers of all varieties of Chinese. Even so, there are some variations in vocabularies in different countries (see example). 

Standard written Chinese can be spoken in Cantonese.

(It is interesting to know that, historically, written Cantonese has been used in Hong Kong for legal proceedings in order to write down the exact spoken testimony of a witness, instead of paraphrasing spoken Cantonese into standard written Chinese.)



Side reading: Language policy of Hong Kong

The language policy of Hong Kong is  兩文三語 (Bi-literacy and Tri-lingualism), which includes:


Written: Chinese &amp; English
Spoken: Cantonese, Mandarin &amp; English


Standard written Chinese is normally referred as "Chinese" (中文) or "written Chinese" (書面語) instead of "Mandarin Chinese".

For spoken Chinese (口語), Cantonese (Yue Chinese, namely 廣東話 / 粵語) is the de facto official spoken variety of Chinese in Hong Kong &amp; Macau. It is influential in Guangdong province, and is widely spoken among overseas communities.

On the other hand, Mandarin Chinese (namely 普通話 / 國語 / 華語) is the official language of China &amp; Taiwan, and one of the four official languages of Singapore.



Further reading


  Before the 20th century, the standard written language of China was Classical Chinese, which has grammar and vocabulary based on the Chinese used in ancient China, Old Chinese. However, while this written standard remained essentially static for over two thousand years, the actual spoken language diverged further and further away. Some writings based on local vernacular speech did exist but these were rare. In the early 20th century, Chinese reformers like Hu Shi saw the need for language reform and championed the development of a vernacular that allowed modern Chinese to write the language the same way they speak. The vernacular language movement took hold, and the written language was standardised as Vernacular Chinese. Because they had the largest number of speakers, Mandarin was chosen as the basis for the new standard.
  
  The standardisation and adoption of written Mandarin pre-empted the development and standardisation of vernaculars based on other varieties of Chinese. No matter which dialect one spoke, one still wrote in standardised Mandarin for everyday writing. However, Cantonese is unique amongst the non-Mandarin varieties in having a widely used written form. Cantonese-speaking Hong Kong was a British colony isolated from mainland China, so most HK citizens do not speak Mandarin. Written Cantonese was developed as a means of informal communication. Still, Cantonese speakers must use standard written Chinese, or even literary Chinese, in most formal written communications, since written Cantonese may be unintelligible to speakers of other varieties of Chinese.
  
  Historically, written Cantonese has been used in Hong Kong for legal proceedings in order to write down the exact spoken testimony of a witness, instead of paraphrasing spoken Cantonese into standard written Chinese. However, its popularity and usage has been rising in the last two decades, the late Wong Jim being one of the pioneers of its use as an effective written language. Written Cantonese has become quite popular in certain tabloids, online chat rooms, instant messaging, and even social networking websites; this would be even more evident since the rise of Localism in Hong Kong from the 2010s, where the articles written by those Localists media are written in Cantonese. Although most foreign movies and TV shows are subtitled in Standard Chinese, some, such as The Simpsons, are subtitled using written Cantonese. Newspapers have the news section written in Standard Chinese, but they may have editorials or columns that contain Cantonese discourses, and Cantonese characters are increasing in popularity on advertisements and billboards.
  
  Written Cantonese advertising banner in Mainland China
  It has been stated that Written Cantonese remains limited outside Hong Kong, including other Cantonese-speaking areas in Guangdong Province; e.g., (Snow, 2004). However, colloquial Cantonese advertisements are sometimes seen in Guangdong, suggesting that written Cantonese is widely understood and is regarded favourably, at least in some contexts.
  
  Some sources will use only colloquial Cantonese forms, resulting in text similar to natural speech. However, it is more common to use a mixture of colloquial forms and Standard Chinese forms, some of which are alien to natural speech. Thus the resulting "hybrid" text lies on a continuum between two norms: Standard Chinese, and colloquial Cantonese as spoken.




Some Cantonese Learning Resources


Cantonese Basic Course: https://fsi-languages.yojik.eu/languages/FSI/fsi-cantonese.html
粵語審音配詞字庫
http://humanum.arts.cuhk.edu.hk/Lexis/lexi-can/
《粵語音韻集成》電子版 http://humanum.arts.cuhk.edu.hk/Lexis/Canton2/
粵語空中課堂 http://www.chiculture.net/0604/html/b05/0604b05.html
粵語網路課堂 http://www.ilc.cuhk.edu.hk/Chinese/pthprog1/index_flash.html
粵語學習中心 http://www.clc.com.hk/
俗語趣談 http://www.rthk.org.hk/elearning/lautinchi/index.htm
妙趣廣州話 http://ifiles.tvb.com/ifiles/fun/fun39.html
粵普字詞配對 http://www.chiculture.net/0603/html/d03/0603d03.html
樂在詞中 http://www.dragonwise.hku.hk/dragonwise_main/index.html




Other References


https://en.wikipedia.org/wiki/Chinese_language
https://en.wikipedia.org/wiki/Bilingualism_in_Hong_Kong
https://en.wikipedia.org/wiki/Written_Chinese
https://en.wikipedia.org/wiki/Hong_Kong_Cantonese