Payments are much more complicated than just who your issuer is. As noted in other comments, connecting the customer directly to the aquirer can lose significant functionality. Pre authorization, installments, card on file and other typical services may be offered differently than expected, or not at all. In addition, Mastercard and Visa still write the rules for industry. If at some point advanced Mastercard or Visa 3ds security significantly reduce fraud, and thus rates, consumers may start paying more for issuers that dont support similar technologies. On top of all of this, point of interaction device support may lag. The latest features from Ignenico and such may take a while to implement, or again may not be supported at all for smaller financial companies.

All that being said, it’s great for consumers to have the choice, and hopefully we all benefit from increased competition.

Disclaimer: I work for a Payment Gateway