I'm for it too BUT it does create problems.
A work colleague booked crystal palace (at my recommendation because they wanted dinner and see the characters). By the time their reservation came up, they had some very tired kids and just knew they wouldn't be able to make it through. So they went to the podium, waited 20 minutes hearing them say "sorry no tables" to loads of people, got to the front and were told they'd be charged as a no show. They asked if they could give the reservation to someone and told no.
So yeah, it's a good thing to make sure people are serious and they cancel but Disney need to be less stupid about cancelling as well