Your username makes me think you're from Japan (in Kyoto), but your comment history puts you more towards USA. Are you a fellow payment industry dev?

well, maybe not fellow anymore, as I left that industry roughly 3 yrs ago ( θ ‿ θ )

As far as I'm aware, Europe, India and the "western" asian countries (Japan, Korea) has a quasi monopoly with visa, but my only industry experience is in the DACH region of Europe. Our numbers were something around 80% visa