PayPal uses P2P as a way to get users to link their bank accounts. Then later, when those users are checking out at a merchant, PayPal tries to trick/strongly encourage those users to pay with that linked bank account, instead of a credit card.

The economics are dramatically different - PayPal makes about 3% of the transaction on a bank account funded payment, they make much less than 0.5% on a credit card funded payment.

So P2P is a loss leader to drive funding mix.