Used to create an outline of your product and model so that you can use the image in any medium and apply a background color or image seamlessly.
But maybe you aren’t in a studio, and don’t have a pretty environment to take the picture in, or you may not have the appropriate environment at all. After all, a dishwasher tray probably doesn’t really belong on a carpeted floor, does it? It doesn’t, and that’s why clipping and masking is needed, in order to transplant a product into an environment where it belongs. This ties to some extent into background removal, but goes beyond it: Maybe some certain things in the new environment should obstruct the picture, to make the shot more natural. That’s exactly what these two things allow you to do; to take the dishwasher tray you have taken a picture of, on carpet, into a well-furnished apartment with all the relevant detailing, perhaps even some kitchenware in the tray, maybe a drop or two of water, making the tray look like the picture of it was taken right there in the apartment, which itself probably is edited together to look perfect.
This may make you think that practically every product picture you see on the web lies to you, but it doesn’t; the product is real, the background is probably real too, but that’s the thing, people love perfect, and people spend money on what they love.
So, in short, even though it may seem to be overkill, looks can, and definitely do, sell products, and a lot of them. In fact, impulse purchases are probably one of the biggest revenue streams that a business can get. And, obviously, the more the merrier.