If you Google around, you'll find that many sites list "normal" residential water pressure as a range, mostly 40 - 60 PSI.
For example, this is typical:
"Water pressure in the District typically ranges from 45 - 125 psi; however, typical residential systems are designed to function best under a pressure of 40 - 60 psi. If the water pressure entering your home exceeds this level, you should install a pressure regulator in the line to reduce the pressure to an acceptable range.
Why say reduce it to a "range"? Why not say "Adjust the PRV to reading of 55 PSI" or "60 PSI".
Is there really no noticeable difference between 40 PSI and 60 PSI?