… I have a modern bike (a Specialized). The tires' rated range is 75psi to 100psi. I usually pump it to around 80–85psi. The tires are 33mm.
https://www.youtube.com/watch?v=7r8f3w89XeM
(watch out, there's a lot of extra stuff in this video about the machine they use to measure efficiency)
The video's result for both tires they tested was peak efficiency at 5 bar. They had a really coarse sampling of a whole bar, so that works out to a pressure of 65–80 psi.
The manufacturer rating is likely a max allowable pressure rating.