A big rackup in the costs involved in a 4500psi site compressor system and holding tanks etc in comparison to 3000psi, and still needing to manage at least one down regulated 3000psi point
Plus the safety issue in managing self filling players to ensure they don't try to fill a 3000psi on the 4500psi point
If 4500 is supplied at a tournament then it's quite often that the site system is at 3000psi and hpac come in to provide 4500psi for the event
The vast majority of players aren't going to use much air per game (especially if m500 now) so the argument for 4500psi is less essential