Someone else mentioned it, but anyone with children that need car seats have a gigantic additional headache. If you rent a car, you're spending however much the car itself costs, plus another $100+ for parking fees at your resort (if you're on-site) and/or at the parks themselves. Even using Uber/Lyft could for all your transportation could be several hundred dollars if you're using it multiple times a day to get to and from parks/Disney Springs, or if you go to eat at any of the resorts (I always like to go to eat the breakfast buffet at Boma and hang out at AKL for a bit).
I think it would be hard for any family with kids to not spend a few hundred on transportation if they're not staying on-site (since on-site would only require transport to/from the airport). I know the Disney Springs affiliates have shuttles, but I don't think they run regularly enough to be useful for people with smaller children. It's much easier for people without kids or small groups of friends -- it's definitely possible to not spend much on transportation, but that would require significantly changing their regular schedule for a lot of visitors.
I wasn't suggesting everyone would automatically have an increase of several hundred dollars, but it would be a reality for anyone renting a car and even for some people who didn't.