I leave my servers running 24/7, thats the point of a server. Also my home automation would be a little pointless if its off.
I did have a UPS, but it died and I have got round to replacing it.
Its all horses for courses, if your homelab is a playground to test things out then turning it off when not is use is fine. But some have live services that you may want at a moments notice and there for having it up all the time is better.