When you fill in the credit card form on the paypal site, you are creating a new PayPal Account.
Yes, it allows you to pay by credit card, but not without creating a paypal account.
see the paypal documentation:
on page 266 there is a screen shot, notice the heading for the form that allows the user to enter their credit card says "Create A PayPal Account". also notice this form is requiring you top enter and validate a password.