Why do they need to change the temperature? I thought it was supposed to be constant.

For the same reason any of them are adjustable? Different usage scenarios, different types of contents?

If you're changing the contents and need to change the temperature, shouldn't someone at the local store be there changing the contents?

I'm not even sure of a scenario where remote control from off site is faster or more convenient. I could see a managers office wanting a connection to them maybe.

Monitoring for compliance is almost certainly easier to manage remotely, which is probably why they're connected in the first place. I would guess control was likely a nice value add. e.g. so someone could respond to an alert remotely

Because you might have to adjust it as the weather/climate around you force you to adapt to it. What temperatures you run in the summer might not work in winter (especially in countries where you get -20C sometimes, and summers are ~25C), and autumn/spring might need adjustments by the day, especially as we start getting more extreme shifts nowadays compared to just some years ago. Heavily depend on the individual store, some are very barebones.