韵/声 Dictionary Organization: Why? I have a copy of《四川方言词语汇编》published in 1987. Unlike most modern dictionaries organized alphabetically (A-Z) by pinyin, this dictionary is organized:

黑白韵
挥堆韵
湖图韵
堤西韵
狮子韵
青城韵
开排韵
豪陶韵
空同韵
侯头韵
骆驼韵
二耳韵
八大韵
天先韵
堂廊韵

and each 韵 is then split up:

平声
仄声

and those are then split up again:

阴平
阳平

and

上声
去声

respectively.
To complicate matters even more: each sections words are determined by the last word (or pronunciation, for that matter) in a given word/phrase/expression.
For instance:
The first word in 黑白韵/平声/阴平 is:

白白
be2 be1
蛋白。
奶娃儿吃点蛋黄黄算了，吃白白要饤到。（饤，读丁，指积食）

and then the following word is

善人伯伯
san4 ren2 be2 be1
旧时乞丐讨钱时对男性施者的称呼。


Why would a dictionary be organized this way?
Traditional Chinese phonology is organized according to initials (声母), finals (韵母), and tones (声调). This is a satisfactory phonological description of Chinese languages/dialects; it's not that different from a more granular description which broke apart finals into glides, vowels, and codas. I can only speculate as to why they decided to do it this way--perhaps that the scholars were describing the categorical distinctions of a dialect group led them to describe sounds in terms of representative characters for contrastive categories rather than descriptions of the specific phonetic realization. In any event, that's how they did it. The fanqie system for indicating pronunciation is a great example of describing phonetics in terms of characters representative of categories.

Many modern texts on 方言 are directed at linguistically inclined people, and they rely on the background knowledge of that general classification scheme. Also, since most modern 方言 descend from Middle Chinese, using the Guangyun system is pretty convenient at unambiguously talking about the phonology of a given 方言. This is especially common with tones. I have read a whole lot of charts like this.

This background knowledge goes beyond just "linguistically inclined people". I know some school children learn pinyin initial-by-initial and then final-by-final. The 注音 system used mainly in Taiwan (also known as Bopomofo, after the first few initials) is organized into initials and finals, though they also break out the -u- and -i- medials (e.g., huang = (h)(u)(ang)).

Now, to your original question. Why in the hell would a dictionary be organized this way? I can't say I entirely know. A few thoughts:


There isn't a standard romanization for Sichuanese that is taught in schools, the way standard pinyin is for MSM.
方言 books (that don't suck) tend to be written by linguists and use traditional linguistic terminology.
Chinese books are usually aimed at Chinese people, after all, so they tend to use Chinese characters rather than romanizations. I will say that I sure as hell prefer a traditional-Chinese-phonology approach over a "I haphazardly attempt to transcribe a language using Mandarin" one.