Most services are on the unraid box. But I had a pi running Pi-hole for a long time (switched to adguardhome) and wanted that separate from the main server in case it went down. Pis boot up a lot faster than my server hardware and then you still need to start the array and mount drives. Having AGH on a Pi as primary DNS means minimal internet outages caused by my tinkering. I was given the 4 and put it in a really cool case that can fit a M.2 or 2.5" SSD and boot from it. So that is NextcloudPi and AGH. The 3 is because my 3d printer is nowhere near a LAN connection and 3 has WiFi. The 4 is sitting next to my router. We won't mention the 1B I've been messing with too...