Because I know what to expect and will adjust my attention accordingly. It won't be what I'm looking for, but I know what to expect from it.

The administration of subreddits has problems, in which some mods (i.e. of SRS) got death threats. Subreddit splits are typically unsuccessful. Exposition and discovery of subreddits is hard. Insightful, rational, two-way discussions are now exceedingly rare, and offensive/tasteless comments are nothing unusual. Popular subreddits tend towards "pop" topics rather than depth.

I am subscribed to DepthHub and TrueReddit but still, neither fully scratch my itch. I think that drawing a firm, clear line and being dedicated to squelching those who step over it will help build and preserve a community. See SomethingAwful, where there's an incentive to stay on-topic and a penalty for being creepy or overly offensive (beyond being just provocative) outside of the forums in which that is allowed.