Actually, the Grand has a free parking lot that we always stay in. We don't pay for the valet. At least, they did last time we were there. I'll double check on it later today. Why do we pay the money to rent a car??? Because we have family in CA that we like to visit (about an hour drive) plus we always like to take a beach day. Honestly, the car sits in the parking lot for the rest of the time but for us, it works out best.
Honestly, even if we didn't have family that we visit (which, we won't on our next trip as they are visiting other family back east while we are there) or a beach to go to, we'd still rent a car. It was so fast and easy and I like having a car to run to the store if we need to. Last time we were there my daughter got an awful cold and we needed motrin and cough syrup. Jumped in the car, ran to Target and had a happy baby again.

I hate lugging all of our luggage, the three kids, car seats and strollers onto a shuttle. And, cost wise, renting a car was cheaper than the shuttle for all 5 of us.
That's why we pay to rent a car. I'm going to read HydroGuys Hidden Time Losses post later. I gotta get off the computer for now, though....