Many reasons most of which you'll only understand if you pay some attention to what's going on behind their scenes.

There are reasons why nowadays pretty much everywhere else on the Internet more content is created all the time than on the Wikimedia projects.

The Wikipedias' "neutral point of view" policy used to mean "we try to treat all sides fairly", now it means "we are writing an unconditional propaganda organ for the status quo". The mainstream media that is accepted as "reliable" as Wikipedia sources just isn't that credible anymore.

Also, when I started editing there, the individual projects were mostly left alone by the WMF. Nowadays the WMF issues intransparent sanctions, up to lifetime bans from all projects, left and right.

I wish someone started an organization with the same goals as the WMF with an actually working system where people could actually enjoy participating.