Complement of result:完 or 好 I‘m currently learning how to form the complement of result and what are the translations of some common compound verbs. My book makes this examples:
• 看完=to finish watching
• 写好=to finish writing
• 吃好=to finish eating(with satisfaction)
• 学好=to finish studying

My question is: why does it use 完 just in the first example and 好 in all the others if the meaning it‘s always "to finish doing smth"?
完 is a verb complement, while 好 is a completion suffix. They are not identical, and  cannot be used interchangeably.

Trivially, 看好 means either look after (kānhǎo), or looking forward to something better (kànhǎo). Here it would be unwise to use 好 as a completion marker, so we always use 看完.

Likewise, 学好 means learn well rather than finish learning (do you ever finish learning, or is it a continuous process throughout life?). 读完 would be more appropriate here.

完 is a more unambiguous particle for expressing completion, while 好 is much more versatile. 完 is also more formal, while 好 is more common in vernacular speech.