For the same reason people still use Facebook and Twitter, despite the algorithm feeding them rage bait; it's engaging.
Sometimes I miss the old 4chan days, when you would argue about dumb shit while also assuming the other person is fucking with you, it creates a weird dynamic where you're in competition to see who can create the most convincing strawman.
Then, some would actually announce they were just trolling, which everyone else knew was a sign that they were actually serious, but wouldn't admit it. Like any of it mattered, since nobody had usernames lol.
I miss the old internet sometimes...