Heh! Fortunately those white primes are good rugged "workhorses"! Even the front element, which is actually a "protective filter", is quite tough!
But the more actively you shoot with one, the more it will tend to accumulate dings in that white paint. 'Course, if you specialize in shooting "tame" things/venues all the time, well sure, you can keep it pretty pristine barring the occasional accidental bump, but for many of us that's just not the way it works!
I was fortunate that when I sold my 300 f/2.8 IS it was just the hood that had noticeable dings. And the guy who brought it just couldn't help but smile at the test images he shot -- he was like "Wow, this takes really sharp shots!", and I smiled, and he left with a great lens and I was left with a pocket full of $$!
Same thing with my 70-200 f/2.8 IS (sold a couple days ago) -- dings on the hood, but the body was in real good shape, a guy shows up, never said a peep about the hood, but boy he was happy chimping his test shots, left with the lens a very happy camper!