Well its the same idea as us getting out of line and getting right back in line. If a celebrity wants to ride again, he can't just get off and get back in line. There really is no other option than to just keep riding.
Think of it like this, celebs are not really "enjoying" the parks. Much of the magic and enjoyment is found in queue's like TSM or Everest, where you and your family talk and share stories. Celebs have none of that. They are shuffled through back hallways all day and have to spend the whole day with a VIP guide. Im sure many of us remember seeing that Travel Channel Disney special with the VIP guide and we all realized how we wouldn't like it, since they are with you all day, even when you eat dinner and stuff. As a celeb, there is no time to relax on Main Street and just take in the view or anything. Just rush from ride to ride.
I know you think they are receiving special treatment, but when you think about it, they really aren't enjoying WDW the way its meant to be enjoyed. So let them have their front of the line access, I got to interact with a talking Mr. Potato Head and they didn't!