I think it has to do with the number of manufacturers, and variations in dimensions. If aftermarket Glock mags were made in Singapore from old coffee cans, they might not work, either. Also, if you use hardball ammo and real G.I. mags, you probably won't have any troubles with your 1911; anything else is straying from what the gun was designed to do, and again, you are dealing with various solutions to the problem of fitting eight rounds in the mag, feeding wadcutters, etc. You also have gunsmiths cutting feed ramps, and adjusting extractors to their magic specifications, and they might not jibe with what JMB and God intended.
Basically what RickB said, there is only superficial consistency across "1911" models, meaning there is no one "standard" like there is for most other guns. Hence some mags work better than others in some guns.