In addition to Dipak's correct answer about the color white, I would like to mention the psychological effect a product image on a plain color background has in comparison with contextual product images shot (for example) on the street.
A plain background will bring focus to the product and allows the user to take a better look at the product. It can reduce any anxiety the user might have about whether or not the product is going to work for them or fits them.
A product can be described to have certain ports and outlets, but user like to be able to see it to make sure.
With clothing, this allows the user to see all the stitches and wash fades (or whatever you call the lighter parts on the pants in the image) more clearly.
Contextual images can enhance any properties the product might have. Like this portable speaker which is highly portable, sturdy and apparently sandproof.
For this couch it's works to see it in a contextual setting. It gives more information about it's size and other properties. It's even an opportunity to sell other products. Just look at that nice lamp! And what a coincidence, it's listed in the suggested products! ;)