Nicely said, we don’t really need anything but the additional equipment is nicer IF it makes tank life easy.Needed, no. Nice to have, yes.
A properly sized UV is a great thing to have for when you need it. But I wouldnt run it all the time unless you have an active outbreak of something.
Adding a new fish, bacterial blooms, diatoms. UV ON.
You dont need a skimmer, or filter socks, or even a sump. But they make things easier. A UV is just another level of that.