The people who work on-site can handle that

That's... not necessarily true. It's entirely possible that nobody wants to touch the freezer's temperature controls because "I might mess something up" or "I don't know how to do that". It's not unusual for a smallish grocery store to have a single employee with a functioning brain and that person isn't always at work. Hell, sometimes there's two and one's on vacation in another country and the other one has a day off and can't be reached by phone. And I'm not saying this to single out grocery store workers as dumb or anything like that, the same holds for pretty much every profession: Most people just switch off their brains at work, they do the exact tasks they're supposed to do every day, and if they need to do something new, that's an impossibility without serious hand-holding. Seen it in grocery store employees as well as software engineers and doctors.

But it's true that the remote control itself doesn't have to be available online, only monitoring does, you can always just send a technician to push the button and change the temperature. But then wouldn't it be nice if you didn't have to send out a technician in the first place?