Without going into too much technical detail, maintaining the electrical aspects of these compressors is a nightmare. Due to design considerations, banks of relays are actually responsible for starting up and stopping the fans on these compressors. Loss of power to the relays is often the cause of the compressors stopping, causing every fridge or freezer cabinet in the store to rise to the ambient temperature with catastrophic consequences.
Supermarkets spend millions on getting the best equipment together for this purpose Old_Geezer and don't buy cut-price equipment. They are in the business of maximising sales and buying cheap equipment would hit them hard if their equipment constantly broke down.
If you want to be certain that the freezers work in a supermarket, shop in Lidl or Aldi, where all the freezers and fridges have sel-contained compressors just like you have at home. No remote compressors and pipework to break down.