[ddq]

In addition, it broadcasts that the sender is too busy with all their important work to spend time refining and proofreading, that you're getting their raw, unfiltered thoughts directly from them, not through an assistant, and that their time is more valuable than yours so the burden is on you to parse their stream of consciousness jumble for precious nuggets of their exclusive wisdom. The semiotics make sense, plus it's just easier and faster.

[lifestyleguru]

The same with medical doctors. Funnily once in financial subreddit someone claiming to be a doctor from maybe Croatia asked for financial or early retirement advice, but the post was a word salad with misspellings and errors. Commenters immediately reacted that their writing is as illegible as probably their handwriting is, by the way the person reacted one can see that's really a doctor.

Some people have superiority complex and reeky pile of irate thoughts in their heads, and you're very lucky if nothing in your life depends on these kind of people.