I have over the past 10 years, used a cup about 4 or 5 times. When I began training with my first coach, we never wore one and just sort of "learned" how to avoid taking shots. That didn't mean that it didn't occassionally happen, but we just sort of toughened up. I really don't know how to explain it.
Years later, I rarely take a shot to the jewels. And it doesn't matter whom I am rolling with either. Could be all out or going light, I never am in the position anymore where that becomes a problem and this is even when in half guard.
Now I DO like wearing a mouthpiece. Especially when wrestling from the clinch to the ground. In the clinch you can get popped quite a bit. On the ground, the mouthpiece comes into play when guys are in cross-sides and are driving their shoulder into my jaw to prevent my turning back into them to recover guard. You're REALLY happy to be wearing one in those circumstances.
Really, I don't use a lot in the way of protection. Even after all these years, I still don't have cauliflower ears.
I'm ugly enough...perhaps that's God's way of sparring me further torment, lol