[fvdham]

In PlanetSide 1 if you wanted to change seats, you had to leave the vehicle
and re-enter at a different side of the vehicle.

This made you vulnerable for a few seconds for snipers and put
a delay between driving and gunning a vehicle, in case you wanted to operate
a multi-crew vehicle by yourself.
It was a penalty for playing solo with a heavy vehicle.

In the case of the bomber, the guy dropping bombs could not
switch to tail-gunner position while airborne, as leaving the vehicle
would drop you to the ground.

The pilot had to make a choice: do I wait a little longer for a tail gunner
or leave without one and run a risk of being shot down from behind by a jet.