Most motorcycles can be leaned over to impressive angles. A rider can make the foot pegs on her machine touch the pavement while moving at considerable speed. The sound alone would be scary enough without feeling the peg fold upwards. If the rider's foot is in the wrong position, she risks having her foot snatched off the peg.
On many street motorcycles, other parts of the bike touch down first, like exhaust pipes, or the side stand. Once I came into a hard left-hander with my wife on the back. I didn't have my suspension set up correctly, so the side stand started to drag even before I was leaned over as far as I needed. As I leaned further, I could feel the rear tire being levered off the ground. This could have become a low-side off the road.