Magpuls/other devices are designed, in general to make handling/grasping mags easier. Mags, while designed to "drop free" never should. In FTF/Malfunction drills, its often taught to retain the magazine for future use/inspection. In tactical reload situations, you will want to retain that magazine for future use should you run absolutely dry, don't, and for future consolidation of the ammo. in those magazines. No weapon, in a combat situation should be shot to end of ammo in a given magazine. It happens that's inevitable. The loss of magazines in shtf scenarios happens. But, its never ideal. Trainig should be to tactically reload/retaining magazines, and malfunction drills, retaining mag's . That's when Magpuls/others come into their own.
Side note, Magpul/training for combat or not, do you want your pre-ban hi/std.-caop mag's to be bouncing off the floor?