Nowadays you'll find that skateboards are laminated several times. Not only does this make the board all nice and shiny, but it means that when one is skateboarding, and one decides to do a grind, or other trick which rubs along your board, the several layers of laminate are going to take the brunt of the attack, and that means that your board won't be scraped at for some time. Hence, increased longevity. On top of that, laminate is a fairly smooth and frictionless surface and therefore allows the board to slide better when doing grinds.