Why do teenagers walk around with their cellphone speakers blaring?

Something I see a lot of nowadays, especially in malls etc., are teenagers who slither around with a cellphone in their hand, blaring out some arb music.
Cellphone speakers are at best, rubbish. You can barely hear what the heck is going on when you play music through them at high volume.

So what's the point?
Does it imply some kind of "street cred" if you can flaunt your cellphone while churning out what sounds a lot like the white noise you get from an untuned TV?

Ever heard of headphones...?