Comment by bux93

The merchant typically uses stripe or adyen or whatever (mollie has a cute name!), a payment service provider or PSP.

The PSP looks at what methods the merchant wants to accept, which methods the user could potentially be using (based on e.g. country by geo IP or some delivery location) and show the relevant icons.

EU users will see schemes like wero or Przelewy24, Japanese customers will see 'konbini' among the icons, and US users may only see credit cards, Apple Pay and Affirm. There are TONS of payment services. Stripe lists 123 of them.

The merchant will want to exclude methods that have high costs (for themselves), maybe they also care about their customers not getting into debt (so no buy-now-pay-later or credit), and some payment methods have higher rates of disputes/chargebacks (e.g. Amex).

In general, most merchants will want to offer as many methods as possible to prevent consumers who have a preference (this week) for using account A over account B from bouncing.