I hosted ad-free invision and phpbb forums for almost a decade before the centralized services started. I do it because I like social media and understand the value of a vibrant commons. I've been working with computers since I was a child so hosting yet-another-app-server is not really that big of a deal and gives my users and myself a place we can call home on the internet.

The out-of-pocket cost is minimal for a small instance, for larger instances scaling issues are going to hit eventually and costs will go beyond what 1-person will bear without complaint.

Highly recommend more smaller instances.

My server costs me only about $5 USD a month and I can host thousands of users without much additional effort (my sites before would usually run to ~10k users).

**Tl;dr we do this because we want to, the act itself is often fulfillment. **