I'm assuming you mean you get kicked after 2 minutes of being AFK in the hub? If so, it's probably because Minetime didn't want people just sitting in the hub for no reason. I don't know for sure though.
That's like asking us to stay in Minetime 24/7 without sleep or food dieing in our own little world. I don't need to describe it.
I know that the afk timer on the hub is 2 minutes, but I'm pretty sure it's 10 minutes on all the servers. Either way, it's there to prevent the server from being overcrowded by players that aren't even playing. I think we can agree that it's still better than not being able to join creative because of an extra 100 afk players.