Threaded Mode

Why don't modern forums and message boards have threaded mode?

Everything is linear mode, this causes threads to go to shit because some guy replied to another guy. With threaded mode you wouldn't have to see useless derailing replies.

maybe it works for mailing lists, but high frequency threaded mode forums such as reddit and hacker news are unreadable garbage. post quality is inversely proportional to how deep into a thread a post is, as they become increasingly self-referential and irrelevant. to make matters worse, they choose to expose all posts by default, in a hierarchically sequential mode. the result is that you have one relevant post (if you're lucky) and then a wall of shitty responses to that post, and then finally another relevant post.