Of course, if you work in an open-plan office -- and let's face it, despite the evidence that it's an unforgivably stupid way to set things up, most of us do -- you can't control the light.
And if you're using a laptop outside of a home/personal office environment (which laptops are presumably built for), you don't have control over lighting either.
For tablets and mobile devices which generally aren't used for working at long stretches, I guess I can see the appeal. But it's really strange to me that glossy is popular on machines people do use for long-stretch work -- and often in high-glare overhead lighting open-plan offices.
(And not only popular, but increasingly the only available option.)