More importantly, ever since SJ took control of Apple, it's been all about form over function, and the glossy screen issue is a clear cut case of that.
As you can see in this triple-confirmed picture, the camera is now behind the glass, which makes it impossible for them to have a matte screen, or the cam image would be nothing but a grey blur.
Is that a valid reason for going glossy-only? No, if function dictated the design, they would keep the camera outside the glass like they did before, but they felt it was more important to go with this design. Just like they think it's more important to have a thin iPhone with a flush surface on the back, than to have a user-replaceable battery.