Good point, but it also depends on how good you are with a gun. Anyone in their right mind that owns a handgun should know how to use it, and practice with it at a local firing range. Plus, pulling the trigger on someone is a huge decision, but if someone is lunging at you with a knife, the decision should not take long because that is a threat against your own life.

I agree. But also this. I've had shooting practice. I've also been trained to use a pistol at close range, when somebody threatens me with a knife or something, and assuming the weapon is still in my holster.
The trick is then, when you actually pull the weapon from the holster to immediately start shooting whilst aiming. This obviously takes some training or otherwise there's a good chance you'll shoot yourself in the foot (literally here).
Overall it's a good technique. I've trained this by using paint bullets (In my actual gun, so it feels very real). My experience is you'll have to shoot no more than 2-3 times before you'll actually start hitting the person. Also, there's the scare effect which makes your opponent stop attacking you when you do this.
Of course, this is a last measure action and should only be used when you're driven in an extremely tight spot.

I wear a gun on a daily basis, and I hope I'll never have to use it. But if I'm ever forced to, I will.