The rides need time to sit, so running them constantly for 24 hours would mean MAJOR maintenance issues and the rides would show their wear and tear much quicker. We complain at the state of things now, and that's with a night off. Imagine how much complaining we'd all do if that happened!
Besides, the park needs the nights to rehearse the dancers, maintain the gardens, decorate for the holidays, clean things, and repair those hard to reach areas and light bulbs. Also, I think the CMs might go berserk at that point.