I don't know about the Max Pressure thing...maybe you would increase for heavy loads (ie trailer...???).
In your owners manual or in the door jamb there should be a sticker that tells you the correct pressure for the front and rear. My Legacy takes 29 for pressure...and the tires look like they need air, but they don't. I think your dad must wear his tires out prematurely, as overinflated tires wear much faster in the center of the tread. On the other hand underinflated (IE 20psi) will also wear irregularly. Ultimately, following the standard spec will improve your tires rate of wear, and your vehicles handling and gas mileage.
IF I were you, i'd just inflate my tires to the recommended spec. and not tell my dad. Go for it! Be a rebel!