I feel like the only real use of it was to allow boards that really needed it a "Must have X karma to post" minimum to weed out bots, and after that there was no point to it.
Chat
A relaxed section for uncategorized discussion. Post a question, share some advice, let us know how your week is going, etc.
What boards really needed it?
I know the hololive board needed it as an "official" subreddit, they would often get people trying to intentionally antagonize people, especially a few years back when they were getting bots from china constantly harassing them on reddit, twitter, and youtube anytime any of their talents tried to do anything.
It's not as bad now, but for subreddits like that, they'd much rather you build up some karma first somewhere like virtualyoutubers where those kinds of bots wouldn't bother posting to anyway, and any non-bots would more than likely get downvoted and not get karma if they were that kind of negative.