The massively oversimplified explanation is that more reflective coatings give a better image quality as long as you don't have reflections. Matte coatings dull the colours of the image a bit and make it a bit less sharp.

They exist, you just did not buy one of those. Theoretically (so in a black room) the clear screen can look better/sharper.

TVs are often designed to impress you when they're on display at the store, leading to your purchase. It should come as no surprise that this is completely different from your home viewing environment.

Glossy screens, vivid and oversaturated colors, etc are a perfect example of this.