Hiking here in dry southern California, I never hike with less than three liters at the start of any day, and for some hikes, I carry up to eight.
Probably because of my SoCal experiences, even in the northern Sierras, where water is relatively plentiful, I always carry at least two liters.
I think where you hike has a huge effect on how much water you carry. And long experience of dry hikes tends to make one carry more water in wetter environments. Does the opposite occur? Has anyone here from a wet area gotten caught in a dry clime with too little water?