I use a pi (4th? generation) to run homeassistant, calendar sync target and a few other random small services on. It's great. It works, it doesn't make noise, it's small, it plugs into USB-C, the power brick is small, too. The SSD I'm storing everything on because I had a few failed SD cards has a larger footprint than the rest of the computer. What not to like? Nothing I run on it requires faster CPU, and the small footprint is worth something to me. Sure, if you have a big house with a dedicated server room/hobby space, you might as well have a NUC/old laptop/whatever.