But Disney's not doing that, either. They aren't throwing people out of the gates because there aren't enough people there, they're just adjusting their hours based on traffic patterns.
I don't know whether I live in your town or not, but I've lived all over the country and I've never been in a place where at least some of the businesses didn't seasonally adjusted their hours. Open air venues like amusement parks tend to do it more often than indoor ones, but bowling alleys and movie theaters, for example, open earlier during times when school is out. You can find a 9:30 am showing of Zootopia during spring break but not the week after the kids go back to school. And I'm betting if you look beyond the obvious in your town, you'll find a similar situation exists there, especially in entertainment venues.
But aside from that, any business would shut down when the revenue that comes from being open just match/exceed the costs of being open. My local Staples doesn't open until 9 while more urban ones open this 8, because they have a traffic history of justifying the extra hour while the one in my town doesn't. It's annoying when I need something early, but I can't blame them because it's their business to run as they need to run it.
It doesn't matter whether Disney makes a lot of money or not, because they aren't a non-profit that needs to zero sum their revenues. If the numbers don't justify being open, then they shouldn't be open.