This isn't a perfect comparison, but ping pong rackets off the shelf don't play that well because no one knows how old the rubber is. The rubber ages, it becomes harder and you don't get the bounce and more importantly aged rubber doesn't get spin like fresh rubber.
That's why people buy custom rackets where you buy the wood or carbon fiber piece, then buy fresh rubber, then glue it together. Then after playing for X number of hours, you can peel the rubber off and glue new rubber on.
I loved a certain shoe, bought many of them, bought older ones on the Bay, then realized the cushion was worn out from age and my feet hurt so I abandoned many, many shoes. Lost a lot of money.