well it's nice that they have the time and dedication to make each flight feel special. It probably helps that there is usually a team of agents per flight (which is usually a widebody, maybe making it feel more special than a CRJ), all working together, instead of just one agent at the desk, one at the door. Also, I think employees in the US would feel a little bit funny doing group activities like that... Japanese people have a special tolerance for whimsical stuff in daily life.

here in the US, there is not much time except for gate agents to shut the door, walk over to work the next flight out before their break.