My guess is aesthetics. I expect codes will vary. My PB said they normally install them only at the deep end with a swim-out.

I specifically asked for them to be installed since there are partially handicapped members of the family that will hopefully be enjoying the pool (currently under construction).

About 6-8 years ago, we asked our PB about that. He said he didn't install them much anymore unless it was for an "older couple." He said that not having them made for a cleaner look.

Our PB got delayed on our project and didn't install the rail until a few months after filling (pool had been prepped for them, though, and bonded). We kinda got used to not having a rail.

Once the rail was installed, however, we found that we really liked it and used it more than we thought...maybe we're older than we think!

A rail anchored in the water can create a problem for some cleaners that get hung up on them, but our Polaris 280 did not have a problem. There's also a ladder guard that can be put on the steps to help prevent the cleaner from getting hung up.

Unless it is a local code, or a commercial pool they are not required.