Here's the way I remember history, starting in 2000 when I was 13:

SMS became popular with us damned kids first. Back in the day each text cost a dime, had a hard limit of 160 characters, and took an age to type on a typical phone 10-key pad. So 1. we had to invent a system to convey body language and non-verbal reactions in text, and 2. we had to abbreviate everything. This triggered the adults' juvenoia something fierce, then the pop culture industry noticed kids doing something en masse and then every product name was SMS abbreviated, up to and including song names. I think they mistook it for slang? l33t came and went at some point in here as well.

By this time it's 2004, Strong Bad is bitching about grammar in sbemails, a lot of the cooler places online are requiring literacy tests to participate, and the adults start going online too, and since many of them didn't learn to type when they were in school in the 60's, they suddenly understand the desire to push as few buttons as possible, and somehow convince themselves they're being cool for doing it.

Hence, you've got folks in their 20's and 30's now who type in a sort of casual longhand, like so.

and people 🧑‍🤝‍🧑 in they're 50s and 60s 👴 who type ⌨️ liek this bcuz 🌵 they can 🥫