If you have to spend a bunch of time retraining staff to use a new POS/updates just so it matches how often you upgrade your home PC so that you can watch YouTube you might not have the right perspective on retail operations/IT. Migration can be a real nightmare and is the reason companies are always digging up addresses, phone numbers and other old info that is no longer accurate but you updated years ago. In addition, each feature your home PC has can make it completely wrong for a store. New, "cooler" stores have new POSes since they, as a company, are new and don't have to protect/access old data... AKA knowledge. There's a real magic that it takes for stores to be successful and updating the POS system to make it where you don't have to see a serial port isn't part of it.
In the case of credit card machines, yes that was an area where we as a nation were very behind Europe and it had the potential to truly have a negative effect on customers.