Time is money, as the saying goes. Buses don't run to the parks from DS. So, you would have to go to a resort, via the bus, then transfer to a park bus or other mode of transport. But...the buses don't start running, with any regularity, to the resorts until past 9am! So, if you get to DS and park, by 9, then go to a bus stop, you could face a lengthy wait. Say you're going to the MK, you would want a bus to the CR, then once at the CR, you would walk over to MK...about a 10 min walk. Going to DHS? Bus to BW (or other Epcot resort), then walk or boat to DHS. Epcot? Same scenario. AK? Bus to AKL then transfer to AK bus. You would need to figure on at least 90 mins total.
Not worth my time to save the parking costs.