iPhone 6 and on edge to edge screen protector question

[iAdamator]

hey all

My wife asked me a question tonight that I have always wondered myself. Ever since the iPhone 6 and onward, they have had those edge to edge screen protectors that actually have the black or white on them to match your phone. They basically look like the entire front of an iPhone.
The question is why do they have the black/white portion? Why can’t the entire thing be clear glass like screen protectors use to be?

 

[Tdosthp]

From what I have seen and used, on some the outer edge/colored portion is a flexible plastic intended to provide a seal and protection around the edge of the phone that cannot be achieved with the glass. It my experience these are not very case-friendly.