The buildup of dirt in the grooves prevents the club imparting the proper spin on the ball. A ball with little or no spin acts like a knuckle ball in the air and doesn't penetrate the wind. Loft and Lie Check your loft and lie. It's something that every professional golfer does several times a year. While most amateurs don' t play often enough to have their lofts and lies checked as often as a pro, it's a good idea to have it done once or twice a year.
Clubs can get out of alignment through normal play.
A two-degree change in loft can mean as much as 10 yards in distance. A properly lofted set will not have any gaps. Maybe their lofts nearly the same. A club that sits too flat will cause the toe to dig in, opening the clubface giving you a slice or fade. A club that sits too upright will allow the heel to dig in, closing the clubface, producing a hook.