Also so that it can make the retailer money. The studio might not want to piss off the retailer, which they would do by pulling the physical copy (or selling it at the OEM price directly). There are cases where retailers will de-list some products in retaliation.

What's interesting to me is that game studios have less to loose here than other OEMs. With equipment like shoes, outdoor gear, or cars, having the physical product out in stores does a lot to sell it: you have to try on shoes, driving a car builds attachment, it's also nice to check the build quality of your tent or whatever.

With games, you generally just have to play it / read the reviews, and you can trial it directly at home in a lot of cases.