Guild Wars 2

The idea behind this is quite simple and realistic. The entrances to towers and keeps if under attack are not usable by the server that holds the location, this would add realism as in when armies were attacking castles, the castles allies wouldn’t run to the gates and be let in, they would then join the battle outside of the walls. This will also make the importance of having people stationed at towers and keeps a lot stronger as they won’t be able to get in to the location.

Adding realism doesn’t really add fun. Standing around in a tower or keep isn’t much fun. As a matter of fact, it’s very boring. That’s why more people don’t do it already. Making it so that players are forced to stay in the keep or tower detracts from the fun of the game.

It’s already not a simple task to get through a zerg and into a tower or keep for defense, but if it were impossible fewer defenders would go to a call for help. At least as the game is set now when someone calls for help there is a chance for response.

TBH if you have a comparable sized group approaching a besieged tower or keep it’s far more effective to fight on the ground than to go into the structure anyway.