xGoldenSCOPExIn all honesty? It's because these specific have a very good reputation. Seriously, the M50's are often recommended to those new to the world of good audio. Whereas AKG, while known to those who follow the audiophile world, is relatively unknown to those who don't.
KailecThe M50 are popular because of its low price point, as well as the emphasis on bass. Most consumers love bass. They judge headphones based on bass impact. The M50 is like a gateway drug. Some people will eventually move on to wanting something more balanced. Some people may want to try out open headphones instead, to see what soundstage means. Then perhaps, people will learn what AKG K701/K702/Q701 is, and may realize how analytical and awesome they are.
To the buyers, you may want to know that the pleather ear pads in the M50 are horrible. They trap heat, and they make you sweat. Get the Beyerdynamics EDT250V ear pads. You gain comfort, lose a negligible amount of bass, gain some treble.