They are connected so they can be controlled and serviced from a central location. These aren't consumer fridges. These businesses basically hire a servicing company and even lease the fridges from those companies. It's more cost efficient then having a guy in each store that basically does nothing all day to fix the occasional problem. And waiting for a repairman to physically come in so they can just reboot or just change some parameters is also not ideal. The problem isn't that they are connected the problem is that people don't take internet security seriously. Like recently some Danish government server got hacked and data from citizens got stolen because a government worker didn't change the default password of his account.