You obviously have no idea of the history of ebay and paypal.   There is no need for ebay to state anything other than it is compulsory to provide a safe payment method for your buyers.

Paypal was an established and successful money transfer service long before it was bought by ebay.  Ebay has now sold it so it is again a stand alone money transfer service.

stawks has posted all you need to know as to why it is compulsory to list using paypal or your own credit card facility.