Because they need remote monitoring. I have experience with HVAC so I'm guessing these are similar: typically outsourced to a third party, typically a VM running on a dedicated server, accessible by Citrix or something similar. Supermarkets don't internally staff fridge repairmen.
You don't need to network the fridge though... You just need a networked sensor...
They could just use connected temperature probes though. no need to connect the power supply of the damn compressor to the internet.