Useless warnings are a great CYA tactic.

THe more of them you have, the more likely it is that there's a warning if something happens. Whether the warning is ever noticed is secondary, what matters is the fact that there was a warning and the operator didn't react to it appropriately, which makes the situation the fault of the operator.

This is partly a problem with our workplace laws.

In the eyes of the regulators and courts individual low level employees can not take responsibility. This is the logic by which they fine the company when someone does something you shouldn't need to be told not to do on a step ladder or whatever.

What this means is that low level employees become liability sinks. Show them all the warnings and make them figure it out. Give them all sorts of conflicting rules and let them sort out which ones to follow. Etc, etc.