Well, that's because in my opinion it is wrong. And whoever taught you that shouldn't be teaching anyone how to fight. Be it Hand to hand or otherwise. You basically said "The more rounds I have means, the more time I have in the fight". While that's all well and good if that's how you want to do things, but the long and short of it is, the longer you stay engaged the higher your chances of serious injury or death. The average gunfight is measured in seconds, and round counts are usually very, very low like less than 7 total rounds from both parties. So in reality you would better off spending the money you would've spent buying the second G19 on some nice, comfortable running shoes.
Shoot and move, engage quickly but disengage quicker. Remember survival is the goal. Not "Winning". Rounds on target from a fast deploy of the weapon, shoot on the move and then keep moving. That is what I was taught and it is how I train.
Just like hand to hand. Aim for the pain then run. Bridge of the nose, groin, pressure points. Engage quick, disengage quicker. Survive.
If you do things differently, that's fine. I was merely stating my opinion