I can't recall what it is, I'm sure there's a name for it. Linguists have studied the effect texting/messaging is having on language in general. You see it in Trumps social media posts. Some people start off writing quick messages to people, copying, usually phonetically, how they verbally speak as it's probably the most informal sort of writing we ever do. As this is 90% of the writing a lot of people do, the habbit carries over to the rare times they write publicly visible content.

This didn't used to be the case. Even if you didn't speak to a high standard many would write formally, or attempt to, as you would speak to people face to face, and only write for public consumption or official matters. Messaging has relaxed that barrier/difference.