y, i cn b lzy 2 somtimes. its 2 mch trbl & 2 borng 2 hit all th kys. mch ezyr 2 use shrthnd.

Actually, it has everything to do with being in the in-crowd. I see it all the time in organizations of various sorts. Sometimes code is used correctly as a shorthand form for complex phrases or explanations, but far more often it's used as a sort of secret handshake for members of the club. It's human nature to want to be "in" and "with it" and encourages insiders to create and use their own language. Interestingly enough, people are usually oblivious to this phenomena.

I recognize only a handful of airport codes but I am familiar with thousands of cities in the world. Countless millions of people recognize the names of these cities and refer to them by these very names (sometime the local name, sometimes the anglicized name). For some reason, to participate in FlyerTalk, one must learn a whole new set of names for these cities. Why? Because it's easier? C'mon! It's an entry barrier, albeit an unconscious barrier, but a barrier nevertheless.