That is not the issue here. The issue is that the webshops aren't the problem code-wise but business-wise. They don't want to maintain their software that hosts

That is not the issue here. The issue is that the webshops aren't the problem code-wise but business-wise. They don't want to maintain their software that hosts the shop, completely ignore private disclosure or simply ignore it. If they don't want to fix it, the next best thing is to warn people about it.