The obvious answer is to deter regional hopping, but there is price “discrimination” for the same product: like $69.99 (US) vs. ~$42.99 (China) for a game. Steam blocks sending games internationally to other players if it exceeds 10% via foreign exchange. Most or all digital game storefronts have an assigned country that supports local currency despite selling the same product. Steam DB exists to compare currencies for a digital game and the differences between there and where you live.

Also: the PS digital storefront is region locked meaning you can’t use a card from one country in another region’s storefront as currencies are different (like Steam really) since they detect the issuing country where the payment method is from. The payment method from let’s say an American CC will be declined on Japanese PS store as in their case they use CC or Debit for age verification regarding games for 18+, does it have to do with different laws and terms & conditions?

Both Wise & Revolut won’t work even though they are multi-currency cards for travel since the algorithm checks the region they’re issued from. In that case, the only way to finalize a region change is buying a prepaid card from that region plus gift cards. That way, you could change countries via digital storefronts (like if the game is 80 Euros in Germany but the same is ~52 Euros in Japan) which would save you money but it’s kind of cumbersome and expensive to set up than buying a game key.