The reason you see that with Glock pistols is that they have 'interesting' ergonomics. The reason you don't see it with M&P's is that a) they're adjustable and b) the ergo's don't suck. Additionally, Glocks have generally 'meatier' grip frames - there isn't a great deal of material that you can remove from an M&P and maintain any kind of structural integrity. I suppose you could remove the backstrap, leave it off and fill the slot with epoxy and it would be marginally smaller, but the ergo's would then be closer to Glock than S&W. Black Box Customs does Glock grip work, they might be able to do something for the M&P along those lines.
