Subscription with Paypal: creating a paypal account is mandatory (and shouldn't be!)

When I try to subscribe with Paypal Express (Membership plugin), it gives me the choice to with my paypal account or if I don't have one, to pay with my credit card. When I chose the latter, the two only options I get is: You have already a Paypal account / You will create one. Thus, I cannot pay with my credit card only. Which clearly an issue, since many people won't care about creating a paypal account.
How can I fix this?
Thank you very much (and sorry if this was answered in a previous topic - I didn't see it, but still...)