Offsite visitors to the Disney parks were parking free at Downtown Disney and taking buses directly from there to the major theme parks.
This created two problems: first, Disney was not collecting any revenue from this practice (and, to a lesser extent and given that one determination for closing the parks to new entries is the fullness of the park's lots, being unable to determine accurately when the parks reached/exceeded capacity); and second, visitors to Downtown Disney were unable to find parking spaces.