The vast majority of Yosemite Valley visitors would not be up and around early enough to do an alpine start (odd to hear that term applied to a hike...but oh well).
I recall one very rainy day while returning to my little mountain tent at the old Upper Pines campground, seeing all the campers with RV's and big tents fleeing to escape the rain. After about an hour, the only campers left were backpackers and climbers. The latter might be expected to do "alpine starts", but not the former.
