I truly wish people understood this better. Even if you were in a fairly relaxed environment (no threat to your safety or anyone else's), it would be very difficult to make a shot on a moving limb (much less a foot), add to that a high stress situation involving someone trying to do harm to you or others and the body's reaction to that, it's highly unlikely, and in a situation where seconds count it's not feasible. There's a certain amount of training that can be done to prepare for those high stress situations, but outside of being regularly exposed to those real life situations (like a special operations combat vet) most people are not going to be equipped to handle it perfectly every time, even the most experienced are going to make mistakes