RSVP?

Do people think that that's on the invitation just to take up space? I've been to several events in the past month where people either showed up without responding or said they would come, but didn't. In the first case, there weren't enough seats for everyone and the restaurant staff had to scramble to squeeze everyone in. Yes, the events were casual, but seating arrangements still had to be made. Of course, the non-respondents were oblivous to the trouble they caused since they couldn't be bothered with thinking about anyone but themselves. In the second case, the hostess purchased extra goodies for the kids and extra food for everyone who didn't show up, thus spending more money than she needed to. I hate thoughtless people!