I think it's like anything, we tend to be comfortable with what we're used to.
I've found my favorite subreddits on Reddit by just typing in various hobbies I have, and then sometimes following to other subreddits that are linked there, etc. For example, /r/amateurradio is by far the nicest Ham radio forum-type place I've ever come across on the interwebz.
Unfortunately though I don't find the astronomy ones particularly useful or interesting for the most part- too much noise usually. And one of the biggest issues with Reddit IMO is the lack of really getting to know people on some places because of the sheer size of how many users are posting.
But then, I am now one of their top users and sold my next piece for Discover based on a popular Reddit comment I wrote, so clearly I'm getting something out of it! But I'll still keep popping into here until the lights turn off, I assure you.
![Smile :)](./images/smilies/icon_e_smile.gif)