If you buy 5 golf swing/putting trainers and each one is guaranteed to save you 2 strokes, then why don't you shoot 10 less strokes per round than you did in the past?!

Fixing the symptom instead of the cause applies in just about everything.

As swing aids go, the swing magic, if you have an OTT problem, using it as instructed works wonders and thats the end of it........but you know how us golfers are, if it works that good with just a little use then if I use it for an hr a day every day then I'll be on tour in no time.........well, no. Using that thing after your OTT is fixed does horrible things to your swing.

Heavy club, instruction is take it back nice and slow and let it just drop thru.....work wonders, but you know us golfers, if it does that much just letting it drop thru, imagine how good it will work if I get it swinging 100mph thru the hitting zone.......and there goes your swing

These 2 examples are not second hand.