Controlled full auto, as shown in the film, when done expertly, is extremely effective even if just suppressing the opponent, while moving to/from an objective. Yes, you can deplete an entire 30 round magazine in about 2 seconds. However, that's wasteful and ineffective. If you watch, especially Val Kilmer, he pops of short controlled bursts of a few rounds in various directions. When done this way, you'll get, say 10 short well aimed bursts per magazine. Very effective.
I saw an interview with US Marine Corps shooting instructors that they use the Heat bank heist escape to demonstrate proper move, shoot, communicate, reload tactics for laying down suppressive fire, short bursts to conserve ammunition, fast reloads, firing in multiple directions in a 360* threat, etc.