Sure, but in the banking world "next easiest option" does not equal "easy option". Switching banks is considerably more difficult than switching hosts.
Plus, most banks are pretty traceable overall. They have document keeping requirements if they want to deal with other banks and governments. No bank is an island.
In an interview on NPR, the lead writer of the paper explained that while there's no shortage of banks willing to process spammers' transactions, they can take down a merchant account in a matter of hours but it takes days to set a new one up so, at least right now, the advantage would go to the defense. (If banks make setting up new merchant credentials near frictionless then we're back to square one. And we know we can't do anything about banks.)