That's because they chose to use Stripe to process payments. You pay by using a debit or credit card. Medium doesn't pay you direct. Nor does any content writing site. They use a service like payoneer, paypal. or Stripe.

Stripe only works with a limited number of countries, so because Medium is using Stripe, it is limited to writers for those countries.

That said, I lived in South Africa. However, I did have a Stripe account from the days I lived in London, and my Stripe Account was linked to my British Bank account.

So the real issue is not where you live, but how to get a Stripe account.