This reminds me of the fact that many foreign subway systems have outer doors (so you can’t just walk onto the tracks) and inner doors. Most people won’t just walk onto the tracks in America but the outer doors address inattentive people, tired people, and people who want to do the wrong thing.

In a lot of places the outer gate is only chest high which isn’t insurmountable but is enough of a barrier to avert 99% of the bad cases. I think the analogy to automatic braking holds.