If using something like snipcart, you can then have a whole shop without you yourself having to maintain or admin a DB, it's all managed by a third party. They do, however, still maintain a DB themselves.
For my product I am planning to create a Stripe-based shop-module, which would allow anyone to create a shop using their own Stripe credentials. This would require some API calls coordinated by our own server and therefore some DB entries, at which point the sites cannot be considered pure readonly from our side.
All of this reminds me of the horrible misnomer 'serverless'...it's servers everywhere. And even the whole 'without DB' moniker doesn't hold up if things get a bit more involved. Maybe ultimately it's worth calling it the "let's try to keep sites as static and readonly as possible"-stack ;)
Thanks for the observation!
At the same time, I think there's true advantages to this approach, so long as you do things right and don't fall into the traps of paying through the nose for things that should be cheap. cough Netlify form handling.
The challenge for Netlify (and my own business as well) is finding a way to capitalise on static sites, so often they will decide on some arbitrary metric and restrict that.
So, while I think the term jamstack may go away, I feel the idea behind static sites probably won't. To be able to make a whole shop, including financial transactions, without a DB in sight is quite appealing imo.
Just don't get suckered into the walled gardens / closed ecosystems out there.