It always seemed odd to me that the card readers are owned by the retailer. On the one hand, that leads to a lot of old or insecure-by-design equipment in circulation as 'not worth the cost to replace", and on the other hand, it tends to lead to a lot of annoying spam calls of "we'll replace your machine if you switch your payment processing to our company."

If the upstream providers provded the readers as a leased service instead-- maybe for a few dollars a month-- they could push out insecure gear in a timely manner more aggressively. Just reject connections from old devices because everyone renting the old model has been sent a new one already. It would also eliminate the price of equipment upgrades as a leverage for competitors to peel off customers.

From what I can tell, the machines are fairly locked to the service providers, and require fairly intensive setup, so it's not necessarily like an unlocked phone where you'd save money by buying a device independently of the service.

Not that I have practical experience with this, but I believe that equipment leasing is the norm in Australia.

Migration has a cost. Many small vendors have razor-thin margins.

Then have the banks fund it out of the savings from reduced stolen card fraud.