I do it because I want to inspire others to make communities like the ones we had back on Reddit. People talking and asking questions and getting answers and in general appreciating the subjects involved. Hopefully, we'll get there.
It's not much time or effort. Low traffic. Mostly I just post the 'best of' I've saved over the years. I recommend doing it if there's a niche you want to see on the Fediverse that isn't currently filled.