As for the club side of the equation, last time I checked only something silly like 8% of the world was a single digit handicapper, and of that 8%, only 2% are legitimately scratch golfers who could attempt to make a living on a playing tour. The reason you don't Tiger's set of irons on the rack, or Sergio's, or Adam Scott's, or pick your favorite tour player is that the clubs they used are designed specifically to not hit the ball straight. You may have heard the term during a TV broadcast "the dreaded straight ball". Every touring pro is attempting to shape a shot on every shot, and with the clubs available to the public, those clubs attempt to do nothing but try and hit the ball straight. The biggest difference is in drivers. For years, Vijay Singh has been hitting various models of drivers that are typically between 6 degrees and 9.5 degrees of loft on the face, and the club face is anywhere between 2 degrees and 6 degrees open. Basically, this means if Vijay were to grab a driver off the rack that was 9.5 degrees of loft, the club face would be way too closed or shut for him, since your consumer version of drivers typically go between 3 degress shut or closed, and there are a few models that are actually 1 degree open. By hitting a club that is too closed faced, or shut faced, Vijay will hook the piss out of that driver all day. When you look at iron sets, the difference is largely in the design of the sole, and the amount of offset. The sole, on the bottom of the club, is typically very rounded for your consumer, this allows him or her to get thru the turf without any trouble, whereas a tour player like a sole that typically is very sharp and digs. As for the offset, offset is put in place to help square the club face at impact to alleviate slicing. Most tour players draw and or hook the ball, so if you have more offset, that ball has no place to go but left.
Hopefully this helps, I can go on for days about all things golf.