Places that use shopping cart software that is hosted / run by someone else.
A store can run WooCommerce or PrestaShop or Open Cart or Zen Cart or many others and the cart information never leaves their server. Name / address and what I bought stays local to them. Picking on Keystone since they are the ones we have been talking about they send all that info to a 3rd party to handle the cart.
Unless that information is clearly mentioned somewhere, I am not sure where I could get it. This is surely not something that a regular support rep could help with. To be honest, I don't know which shopping cart software brands are self-hosted and which ones are operated by a 3rd-party myself. I will have to take your word for it and trust you gave me the correct info.
Some want more info then others. But keeping it internal by running something like BTCPay is still better.
I can't help but to think of Ledger in this situation. All it takes is one unknowledgeable or malicious employee to destroy your reputation forever. Ledger wasn't just affected by the Shopify breach. Their employees caused a similar incident themselves. Self-hosted or not, your data is still sitting on a server somewhere that could get hacked with enough motive and incentive. I agree that it's surely more rewarding attacking and breeching the defenses of a 3rd-party company, which handles such data by millions of customers than to attack one individual business.