My wife and I were in California last year early summer, we made reservations for Sequois and Yosemite of corse but thought as we came on east over the mountains to 395 we would have no trouble finding a spot each night..........wrong..... during the week days " tues, wed,thur, we went to 8-9 campgrounds looking for a spot hookups or not we didn't care, we ended up staying in a hotel in Bishop CA for a couple nights.
to answer your question yes camping is really taking off seems to me and we make reservations every time we hook up to the camper now.