If they didn't exist more people would just enjoy airguns for what they are and stop looking for one than can replace a PB.
Truth is, if PCPs never existed, there is a good chance neither would any other air gun. PCPs have been around since around 1580. The others from the 1800s.
It would be interesting in 50 or 60 years to see what, if any, PCP gun stands the test of time.I ain't gonna be around to see it anyhow...