[Gwathagor]

First, I agree that making Rings of Power was probably a lot of work. Not sometihng you do for fun.

Second, you can't just go around handing out rings to everyone. It reduces the coolness of having one, because it's no longer an exclusive club.

Third, it's easier for Sauron to control the races of Middle-earth through a few powerful subordinates who will theoretically (didn't work out, of course) do your bidding to the letter. It's less management for the big man. Delegation is an essential leadership quality.