As others have said, many customers come into shops with a preconceived notion of "mo air is better". Two shops ago this attitude was worsened by a coworker who rode Vredesteins at 140 PSI and his being in sales there was not much I could do. That he was a faster rider then I only made it worse.
Even on my tandem I never go above 110 PSI. And I prefer supple tire casings over thick unyielding ones.
Andrew R Stewart
Rochester, NY