Unfortunately it's not your call. If you're able to transfer, you should as long as there is an open seat for you. And if there isn't, you shouldn't have been loaded. The drivers that allow you to remain seated should have not, unless you told them you could not transfer. If someone tells me they want to remain seated, I inform them that if you're able to, we would prefer that you do so for your own safety. That is usually enough to persuade them. The bottom line is that if you can transfer, you should.