Imagine they where internet exposed due to simplicity. It will take longer than three weeks to set this up. Not for you but imagine you are a store owner with 0 IT knowledge.
The issue is this needs to be handled centrally by the parent org also. They have IT of course but they usually do POS and desktops/servers.
The OT/SCADA systems are usually totally separate and not touched by the white collar IT systems.
Imagine developing a control system for a professional freezer and designing it so it can be directly exposed to internet due to "simplicity".
Want something simple? Don't connect it.
ICA is franchised, so stores are owned and run by operators. The central company offers some services, but a lot of the decisions comes down to the individual stores.