> Plus, why should "GUI" get a pronunciation but "CLI" be neglected?
It's probably because the person who made the acronym or initialism had wanted it to be pronounced a certain way and chose a sequence of letters to achieve the desired result. Of course, the speakers of the letter-group will later decide when and how they will pronounce it!
Acronym: a word formed from the initial letters
or groups of letters of words in a set phrase or
series of words and pronounced as a separate word [1]
Initialism: a set of initials representing a name,
organization, or the like, with each letter
pronounced separately [2]
It's probably because the person who made the acronym or initialism had wanted it to be pronounced a certain way and chose a sequence of letters to achieve the desired result. Of course, the speakers of the letter-group will later decide when and how they will pronounce it!
[1] https://www.dictionary.com/browse/acronym[2] https://www.dictionary.com/browse/initialism