So interestingly - the web shops you’re talking about do want to maintain their client data, and do expect it to be available “forever,” somewhere. The payment processors absolutely do at a minimum. Some of those layers are highly hardened.
While the particular Etsy clone or t-shirt of the day, or customized shower curtain site will certainly come and go, it’d be an entirely different problem if visa, PayPal, stripe, swipe, or whatever payment processor packed it up and went home at random.
We need the foundations/infrastructure to be built to last. People need to identify which kind of software they're making and treat the infrastructure as unchanging. Changes in the basement need to be carefully considered with a default stance of rejecting them unless justified by reasoning that has a time horizon of many years.
While the particular Etsy clone or t-shirt of the day, or customized shower curtain site will certainly come and go, it’d be an entirely different problem if visa, PayPal, stripe, swipe, or whatever payment processor packed it up and went home at random.