For instance, in China WeChat Pay only charges 0.1% above 10,000 RMB (from what various articles say). Square is not even in the same category, charging 2.6% + 10¢. And you don't need to buy any equipment to use WeChat Pay; you just need to pull up a QR code on your phone.
This allows people to on-board to WeChat Pay easily through online banking. They also have way less KYC hurdles, so people can go from signing up to sending money in minutes.
US online banking is eons behind China, and almost any other country. So many online banking systems in the US are prone to unauthorized access, which makes on-boarding and security highly inefficient.
The big difference is how fast and cheap these standardized bank-to-bank transactions are; with USA lagging behind in this area somewhat. In USA a wire transfer is more expensive than a credit card payment, in China, EU, Russia, etc it's cheaper than a credit card payment.