I am one that uses at least a UV. When I bought my Sigma 100-300 f/4 which has a 82mm thread I went a while before I got it covered because after shelling out that kind of money I was a little tight. I didn't want to buy a cheap filter just to cover it because I was concerned about the IQ also.
But the price of a quality 82mm
Anyway, I was very uncomfortable that whole time it was bare. I mean' if one was in a studio why worry. But I notice after just a few minutes of being out on a norrmal shooting day the lens attracts a lot of dust. And I hate touching that lens with anything, but thats just me.