This is a 2-in-1 question, I suppose. I type the way I do. I’ve always typed this way, but I’ve noticed when interacting with people (not on here) that people always think I’m far older than 19. They think I’m in my forties or fifties.
Also, I tend to type using full stops, which people may think are rude. When I’m typing a full sentence, though, I end it with a period. If I say, “He’s being an asshole,” (with a period), I mean that as a fact, not out of anger. It just happens to be ended with a period since it’s a sentence.
Because those of who grew up communicating a lot via the written word stopped feeling beholden to type using classic grammar rules like ending every sentence of every communication with a period no matter what.
The entire purpose of language is to express yourself, and people started noticing that their texts sounded friendlier if they sounded less abrupt, so they started typing that way.
You type according to traditional essay writing rules which is how older people learned to write, younger people learned to focus on producing natural sounding language and conversation.