We have stayed at several places, and they all had Bed Rails.
I have tried to ask for them when I checked in, but they ask you to call housekeeping.
When I called housekeeping, I always asked for a specific number of bed rails.
When my children were younger, I always asked for one bed rail for the end of the bed, and 2 bed rails for each open side of the bed. The bed rails I always got were not very long, so when the kids were young I asked for two for a side, so it would cover most of the length of the bed. I was always scared that even if the bed rails protected them from falling out of bed, they still might hit there head on the night stands.
Housekeeping always brought the requested number of bed rails, and I slept a lot better at night setting up the kids bed that way.