My commuter has 27 speeds. On a typical ride, I'd use about 10. Depending on the wind, I could use up to 15. My road bike has 30 speeds and I've used 28 of them (only ever avoiding the most severely cross-chained gear combos).
It all depends on your terrain, of course. On flat ground, I could get by with 1-3 speeds. The hillier it gets, the greater range I want and I like my gears closely spaced, hence 27-30 speeds.
Most pros run double cranks so will only have 22 gear options max ( 2 x 11). I'm guessing they used most of them, too, when riding in the mountains at least. And most (all?) leave on the inner ring even though I doubt they ever shift to it on a flat stage.