In reply to Marcus Tibesar.

Developers of payment gateways are remunerated by the payment providers/collectors on a revenue share basis, in this case, it's Stripe.

But those agreements are usually time bound (at about two years). However, with this new "private label" payment gateway, WooCommerce/Automattic has a stronger position in negociations for a longer time period or even an unlimited one. The reason being they could try to switch their payment collector if they don't get the period length they would like.