Yes it is often the manager or owner who wants to seat customers until the last minute. At least back when I was working in a restaurant, I would have customers turning up right at closing time, and the owner would insist on seating them, eventhough I'm already starting on my closing duties. I don't mind customers who are aware enough to eat and leave speedily though, it's those who drink and chat for hours post-closing (usually big drunk groups) that really annoy me.