From my experience in a restaurant, those large commercial rooftop refrigeration/freezer units need attention several times a year. It's rare that your home fridge would have trouble that often but commercial units are more complicated and in a harsher environment. And supermarket installations are probably even more complicated.
Routine service and maintenance doesn't require net connectivity to schedule.
Agreed. I was just addressing that it's not exceedingly rare to need to get a tech out on site to address something. Should the manager be on top of this, checking temps on all the cases every day? Absolutely, but I can see the argument for a more automated system of monitors/alarms that can get a tech dispatched before the manager has even noticed the problem.