Like how pretty much every file extension that is a word, is almost a word, or is even reasonably close to something you could say like a word is pronounced.
A .jpeg/.jpg is always a "jay-peg," an .mpeg/.mpg is "em-peg" (and "em-pee-gee" will definitely make people think "miles per gallon" instead), .wav is just plain "wave," .txt is always "text" (...and if anyone says "a tee-ex-tee file" that person is definitely a robot/alien in disguise, and probably not the harmless or benevolent kind), .gif is always "gif" and you rarely hear anyone argue for "G. I. F." even when the argument over pronunciation comes up (between the vast majority who says it like "gift," and a loud minority who claims to say it like the peanut butter brand but are mostly just being contrarian on the internet aside from like... one guy) because both sides know even if only on an unconscious level that to do so would be The Wrongest Way, .doc is... well, "doc," .docx is "doc-ex," and so on.