If a person is poor and doesn't use/have AC in his own house; why force him to travel in AC for one day and shell thrice the money? IR should increase AC coaches slowly and proportionally as the country advances. Some routes are more conducive for AC travel; other aren't. For eg, Sure as heck, Lucknow-Chhapra dedicated trains doesn't need TEN AC coaches when there are dozens other trains running on the route. IR needs to do a check as to which classes have more WL's and then decide. Sometimes, trains have SL completely booked and AC still relatively empty which equates to lesser demand for AC on that route. It's a simple question of supply and demand. Of course, since IR is a monopoly, it can theoretically throw away any "social service" thing to the wind and make just AC coaches if it wants.