I asked my partner, who is a photographer, and she said that it really makes it easy to swap backgrounds at a simple level. You load up the photo, select "all but the green color hue" and then copy it on top of a background image. Because it's one standardized green color, it's a 10-second job to select all but that one color. Without one background color, you'd have to do manual select all the colors and/or shapes by hand (AI and some tools can help a bit), but it is painfully time consuming regardless.Thank you for the explanation! I thought the screens were a bit more shine-through (like a thin t-shirt or something).
The shade of green is specifically chosen because it apparently has very low chance of showing up in skin tones, clothing, and hair. The more you know.