On LD trains, some coach attendants assign seats based on destination, usually for the convenience of both the crew and passengers. If you're going all the way NYP-MIA for example, you wouldn't want to be put with passengers only going from two midpoints in the middle of the night, waking you up with luggage, doors, and such. It also helps the crew manage who is getting off where to not have any paassengers miss their stops.Are they assigning seats in coach now? Has been a while since I've been anywhere but business class or higher. Too many AGR points....