As already noted.....you can park there while enjoying the facilities of that resort. But....those facilities and amenities do not include parking for the day while you head to a park. If you wish to do that, then pay to valet park. If you are valet parked, you are free to do what you wish and go wherever you wish to go.
Can you imagine how hard it would be for those who are paying to stay at the resort, to find a decent parking spot because those who wanted to avoid the masses exiting the park decided to leave their cars there for the day?? I know it's happened to me while I was at BW. Huge number of cars there during the day, but man, you should have seen the line of cars pulling out around 9:30 or so...after IllumiNations ended. Hmmmmmm.
But again, if you just want to park, selfpark, while you eat, that's fine. If you wish to spend some time at a park, then be considerate and pay to valet park.