There is a pretty significant systems engineeing effort to integrate the battery performance with the motor and power electronics. Tesla does a fantastic job in

There is a pretty significant systems engineeing effort to integrate the battery performance with the motor and power electronics. Tesla does a fantastic job in this regard and that is likely responsible for their high efficiency. You lose a lot of ability to do the integration in an optimized way if you have to design around different batteries. All that to say there is a lot to be gained by not doing a battery swap system.