Or why only apple monitors are glossy? This have anything to do with color fidelity?
Do applying anti-glare film reduces image quality and color spectrum?
Apple is not the only manufacturer who provides the option of glossy monitors. Because you see rows of iMacs in the Apple store with glossy monitors does not mean Apple is the only manufacturer who provides them. Also, not all Apple monitors are glossy.
Pros for Glossy Monitors
Cons Against Glossy Monitors
I prefer a glossy monitor for my main working display. I have an anti-glare as my secondary monitor, so I do have a chance to preview the images somewhat as others will see them. These are both Apple displays. Both are color calibrated and I have not been disappointed with either. On my laptops, I have been far more pleased with the glossy display than the anti-glare, primarily because when I show images to others on the laptop, they display to better effect. Many prefer an anti-glare display on a laptop because you cannot control the lighting around where you use one, but I've been pleased with the added perceived brightness and besides, I don't do any final post processing on a laptop.