I don't know.Unrelated: Why do you always type one sentence out then press enter on your keyboard?
I think it originally came from typing a whole lot of crap on ICQ in the 90s.
I also try to avoid wall of texts at almost all costs - you see on average, GAFs text lines are about 2-3 times longer than a word document and 4-10 longer than a newspaper, this can make reading them a bit taxing; line breaking is not ideal, but I think it makes for a quicker less error prone read and it also render itself better for skimming (and that's a good thing in a web forum if you ask me).
But once people started giving me shit about it here I just doubled down on that because I'm a stubborn dick.