If I see that people are waiting, I tend to get in my car and drive off as a courtesy. I can do all my other stuff elsewhere like a loading area or something. If I have a parking ticket which still has time on it, I'll usually offer that to them too.
Then again, I find that being considerate to people around me ends in much more pleasant interactions with them rather than annoying them for no real reason.
The only voice of reason so far in here! Unless there is a genuine reason to wait in the space I'd be considerate that it's a busy carpark and get out of there so others can go about their day as well.