It's likely this was a conscious business decision; PayPal derives value through its brand, which is lost to consumers (buyers) using the platform if the platform becomes a white label solution.
PayPal wants customers to know they can pay with PayPal at business/merchant X, not just their credit card.
Indeed, Paypal doesn't want you to pay with your credit card, and won't let you change your default PayPal payment method. You have to go through a process to select it Every.Single.Time, if you remember, and if you overlook to do it - well, what do you know, PayPal just saved the CC fee...
PayPal wants customers to know they can pay with PayPal at business/merchant X, not just their credit card.