Here's the problem, and any Chicago area beer drinker can back me up. See, about ten years ago, they tested beer in plastic bottles instead of glass at sports stadiums. The idea is that it would take care of the, "It's a tasty refreshment, and a spontaneous weapon!" angle, as well as a bunch of other bullshit I don't remember anymore.
Here's the problem -- plastic will leak some of its chemicals into drinks. Now, if you have something overpowering, like Pepsi, there are so many other flavors and they are so dominant, you don't notice. But subtler flavors, you will notice. It becomes worse if the drink is acidic. Since I insist on lemon flavored teas, the plastic bottles give the tea a "yuck" dimension I really can do without. Not only can beer drinkers back me up, but so can wine aficionados who've run across certain box wines. Those box wines would be a lot more acceptable if it didn't come in a plastic bag inside that box.
So that is the reason for the glass bottles. They don't corrupt the flavor of the drink. They have one other advantage, in that the mouth of the bottle is wider. CHUG CHUG CHUG!