Good question and yes, that option is open and available. We first want to open the biggest channel possible for easiest STEEM/SBD spend.
We will also attract merchants and sellers from outside of Steem community and thus the reason for accepting VISA/Paypal. However, STORS token spend for upvotes will at first require a Steemit account to be setup so ideally, new user signups should increase.
It is awesome that you accept VISA/PAYPAL!