Complement of result:完 or 好
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.