Same reason that actors can cock Glocks, continue to shoot on an empty mag, fire 346 rounds without reloading (unless it's convenient), and disassemble a Beretta 92 one-handed via some manner of ninja voodoo.
Might also be the same reasoning behind movie cops shooting fleeing suspects, last I knew that was a no-no.
It's showy, flashy, and exciting, especially considering that the a lot of the people who enjoy the movies are not really gun people.
Me? I try to ignore all these things and just enjoy the show or movie. If you're calling out everything that was done wrong after every movie shoot-out, it won't be long until no one wants to watch with you anymore
Guns must be aimed in order to hit things, even at close range.
What, you don't have any of those newfangled heat-seeking bullets?