Not defending Disney here, but I read a while back that they set the hours based on resort capacity and estimates on crowds. Supposedly they set the hours so you can do 8 major/rides attractions in one day, if I am remembering correctly.
While I agree that night touring is fun, it's possible that the crowds just still aren't there for them to justify regular hours later in the evening. I read a thread on the Resorts Board that even with POFQ closed, there is still availability in June at 4-5 Disney resorts. So they aren't full.
Yeah in 2000 and earlier they were open till midnight and later. They also experienced record crowds in 2000 and possibly 99.
Again, not defending the decision, just trying to be informative. Personally, we can't handle a commando schedule, and our kids are still young enough that late night hours aren't a make-or-break deal for us. Maybe it is for you.
Good luck with your decision.