If you think about it, credit companies like Visa/Mastercard/Amex have a very strong incentive to corner the market. It is very likely they want to build up an internal eco-system like Paypal, where customers must buy and sell through their services but never have custodianship or the ability to transfer Bitcoin outside of their network. They get the best of both worlds - customers fund the acquisition of an asset, they get to whack on a bunch of fees at different stages of the transaction (buy fee, holding fees, selling fees) while getting control of a cryptocurrency that is directly competing with them. They are already experts in security so the rest of it should be relatively straight forward for them in terms of creating a new revenue stream.