A lot is the rise of digital communication/texting/social media, the rise of emoji's, and keeping in mind the medium, it's to shorten everything, using gestures and symbols as/in place of actual communication. That's why everything is shortened, and acronyms.
For instance, WYD is different at 11:34 PM from a woman, than from that same woman at 2:47 PM, (usually) it's the context, and ambiguous nature of symbols and gestures. Hey vs. heyyy, hiiiii, helooooo, hello
A lot is about how can say the least with the least amount of effort, and also kind of protect yourself, digitally. Millennials and Z minimize their effort and involvement, even when they are really invested. We talk about double texting, and late responses, we talk about what an exact emoji means, on some level is fascinating, on another it's bizarre, and disconnected.
Like, if I text someone, it's usually a well thought out, direct, unambiguous, maybe three sentences, if someone "ghosts me" on that, you are going to feel a little rejected. But, if I just texted WYD or WYA, it's way less investment, and far more interpretive.
I used to always wonder why people text "WYA", or "WYD", (almost never do they actually care where I am or what I am doing) but it's almost like a feeler, like are you there?