RWorld has a lot of clubbing traffic, especially on weekends and also whenever their day club is open. These people don't gamble and perhaps there is no way for them to get their tickets validated. It is to keep that flow going perhaps that they decided on the free parking.

People who play get high enough level player cards to be able to get free parking.

For some time now the RWorld parking machines haven't been working properly with hotel room keys and at least at the entrance with player cards, but the lots are pretty full at least the first few levels. Looking around the casino it doesn't seem like they are doing that badly, not full most all the time like Wynn or Venetian/Palazzo, but not starving.