Not really. First I don't know many nights when the parks are open 3-4 hours AFTER 9pm, unless your talking about special ticketed events. Second, we close down the parks (I agree I don't see why people would leave the park 3-4 hours earlier than close. The same wasted money for sleeping in applies equally to leaving early) so we are getting both the the benefits of the rope drop, AND the benefits of the later hours of the park. Even if the park's best time is at night, you are still "throwing away" the time for rope drop if you are sleeping in. Your still using potential time at the parks which you paid dear for....to sleep in and do nothing.
Third, even assuming for the sake of argument that the parks were all open until 12-1AM, being that WDW's prime demographic involves families with young kids, most of them are not keeping their kids out that late. Doesn't mean their aren't some that do, or some adult only groups visiting WDW, but they don't matter in the broad scheme of things, as you don't design park features for the minority of your guests.
