Equifax has had a terrible rep as a service long before the hack. Even john oliver had a segment on it before the hack happened, on how an egregious number of reports are grossly innacurate (like 40%, i cant remember). That has to be bad even for the banks: bad credit reports equals bad loans.
Regulation tends to decrease the number of players and increase the size of the incumbents, particularly because it puts requirements that can only be done with big bucks.
But none of that has anything to do with securing Americans' data. Also, even if that 40% figure is true, which I doubt, it's not like banks are going to care until they run out of people they'd like to loan money to.
Meanwhile, regular non-bank Americans get screwed in ways that could have been mitigated by regulation. In economic terms, that's called an externality, a concept which is covered in any reasonable Econ 101 book. The foolish solution to a market failure is more market.
Regulation tends to decrease the number of players and increase the size of the incumbents, particularly because it puts requirements that can only be done with big bucks.