They get in the way under two conditions.... 1 - you're goin REALLY frikkin fast & have some serious lean angle going or 2 - You're not using proper technique.
I have stock footpegs on my ZX6R. no rearsets... I got to the point where I used to drag them alot until I learned how to ride fast with good technique. Now I go faster, carry more cornerspeed and even more lean angle believe it or not, but I haven't dragged my pegs in a long time. The way I do this is i get OFF the seat, use proper body position, use positive steering inputs (faster turn-in actually results in less lean angle through the turn) and get ON the gas nice & early. This raises the suspension and gives you more ground clearance.
On my EX I have woodcraft rearsets (came that way). I dunno if i'd scrape them before the exhaust or not. I've dragged my headers before, both sides. Think i've posted the pic before, but i've got a shot of me exiting turn 10 & hitting the NASCAR transition at NHIS w/ sparks behind my rear tire from the header grazing the pavment. I had no idea I even did that untill one day my teammate said to our teammates "****, it's fun chasin Pete around w/ him sparkin up everywhere". Since then I've raised the rear suspension to where it's actually supposed to be & that helped alot... I'll also probably trim the crossover pipe and push the headers closer together & further underneath the frame. (
sparky pic, for those that haven't seen it ;D)
Early in a rider's career there comes a point where scraping footpegs becomes kind of a bragging right cuz it means you're gettin the bike leaned way over... But then later there comes another point where you realize NOT scraping footpegs is better, cuz it means you're doing it right.
But with that said, I woudln't be suprised one bit if the top experts that still have stock pegs have ground a bit off of them from scraping the pavment.