But the pirates one doesn't stop you falling out (though you'd have to try hard to actually "fall" out.
The pirates (and small world) bars are just a little thing stuck on the top of back of the seats in front of you. They do not move over your lap in anyway whatsoever, meaning that if there's enough room to climb in, then there's enough room to climb out again.

It's just there for holding onto during the pirates drops and when you bump into other boats - nothing more than that.