When borders are removed and trade increases, new ideas and new technologies emerge, enabling creative entrepreneurs to turn these into new products. For payments in particular, having the same standards boosts innovation, which produces network effects. The entry of a new merchant or consumer increases the value of the network for all participants.
When many people use the same internet payment method, for example, more e-merchants will want to offer this to attract more customers. And when these customers find the payment method convenient, they will tell others. This word-of-mouth advertising leads to more use of that payment instrument. This creates economies of scale, lowering the cost of each transaction.