I was upholstering a staircase in a very ornate home last Thu/Fri for two of the most brutal asswipes.
The two cats in this house got no rest whatsoever. They were champion breeder types and the ladies head was completely up their butts all day.
One of the first curiosities I noticed was the Plexiglas fitted to the pickets of the stairs and upper loft/ landing. Looked nice actually.

After about an hour or so on the job, I concluded that without a doubt, this clear barrier was an attempt at keeping the cats from committing suicide.