Reddit is actively trying to reduce the average age of their userbase. The mobile app, and forcing kids to install the mobile app, is a big part of that effort.

Getting teenagers in high school addicted to Reddit is a huge part of their strategy, and it's very evident in the way the front page content has shifted in the last decade.

The bigger issue is that while a lot of older users remain in the niche subs, I find that there aren't great alternatives to Reddit for threaded sub-specific commentary.