In rumborak's case, his being a party of 5 made it more difficult, since most tables in your average run of the mill restaurants are designed for 2 or 4 people, so a party bigger than 4 often has to wait for one of the few larger tables to open up, unless it is kind of slow and they can pull two tables together or something like that.
As for asking people to leave, that is generally not done, nor should it be (although I think anyone who would get offended by that needs to get a grip, and that speaks to how easily people nowadays look to be offended, but that is whole other story...). I get that "camping out" at a table for a long time could be considered rude, but what if it's two people who haven't seen each other in a while and they get caught up in conversation after dinner and end up sitting there longer than they had intended? You don't always know you are gonna keep chatting away for a while after dinner.
Now, if you sit there for a long time past closing, then you are kind of a dick, especially if you see the rest of the place is empty.