The benefit is the same as making websites remote controllable. A person then doesn't have to drive in to flip a switch, which means fewer people are needed to operate more systems, saving the company money.
Presumably the grocery stores are already staffed by at least one employee capable of flipping a switch, no?
Switch to do what? If food is in it you can't change anything. If food isn't in it then why is it running or why wasn't it defrosted when it was emptied?
If you home refrigerator could be defrosted remotely, in what scenario would you ever do that?