Why in god's green Earth do dungeons have a timer?

[ispano]

Don't the timers disappear when you finish the dungeon? So you can spend the whole time RPing in your dungeon then. I know when I beat Twintania for the first time we spent some time taking screenshots after the kill and there was no timer. You also didn't have to leave the dungeon either.

At least in normal dungeons, you get booted out after 5-7 minutes if you complete it.