Poor-quality mods and admins
Forum moderation is probably the number 1 reason that people would escape them if they could. If social media runs on nameless mods, many of whom work in sweatshops that oftentimes are offshored to Africa or India (especially after certain scandals like Facebook’s moderators having PTSD), forum moderation is similar to that of a fedi instance or bad Discord server: one guy is the admin, he appoints mods, and everyone does what he says. It’s his forum, his rules. This structure in many cases leads to bans, bad decisions, and many more insane incidents that after a certain amount of time, end up with users trying to provoke the moderators on or off-site (as seen with SomethingAwful’s many offshoots such as Something Sensitive).