I think they probably do have a lot of customers that want less over the top theming. That's one of the reasons that some on this board cite for NOT staying at values. People might want over the top theming outside in the lobby or pools but not in their rooms. Neutrality is a big part of the general budget boutique movement, I feel. It's supposedly the same reason for hard floors and white bed covers. Guests see it has a cleaner/more modern look. I don't personally get it but I have a lot of family and friends who don't like the idea of staying in an over the top themed room. These people want to only spend so much but they want to feel like they're in a "classy" hotel.
And if Disney didn't like running hotels, they wouldn't have started to do so to begin with. They put a huge amount of money into attracting people to stay on property. It's because it's a huge money maker for them. It's like Vegas- it's less about the income from the hotels and more about the income the booze and food options generate. If you stay off property, you're way less likely to eat every meal on property.