In that case it's just a tradeoff between convenience and security, it isn't because it would be too technically difficult to isolate the systems. Whoever installed them could isolate them if there was no reason for them to be connected to the internet. I doubt most grocery store managers understand the precise engineering behind their freezers either, but they still buy them.
Very likely they were sold on these internet-connected systems without being told about the drawbacks, which is sad.
Very likely they were sold on these internet-connected systems without being told about the drawbacks, which is sad.