The tech isn’t too hard.

Getting billions across many different cultures to trust you with money is hard.

They have numerous competitors, from American Express to PayPal. Even crypto could be a competitor. But they have trust problems, are too expensive, or provide no benefit to the purchasers.

Credit cards in general are hard to disrupt as they pay a substantial kickback to the people who would otherwise be adopters of a new technology.

As a high income, technologically savvy, globally mobile person, I am who a payment company would need to flip to drive broad global payment adoption. Unfortunately for them, credit cards are enormously valuable to me as is due to points and perks.