Maybe. I think at least part of the reason is political though.
Nobody wants to be the person who scraps a security policy and then has a terrorist attack happen as a result of their policy removal. Not politicians, not TSA higher-ups, nobody. That's a career-ending mistake, no matter how unlikely it may be.
Not to mention that it's probably not a particularly popular decision amongst the public. Maybe it's security theatre, but people like it.
I think it'd be pretty easy politically, at least from a conservative (i.e. not Republican) standpoint. Argue that DHS is government waste and can't stop shit (point to the numerous studies done over the years of them being able to stop all kinds of shit from going through). Let things go back to the way they were: airports hiring private firms to do security.
This would never happen in today's climate though since both parties are pro-big government.
Nobody wants to be the person who scraps a security policy and then has a terrorist attack happen as a result of their policy removal. Not politicians, not TSA higher-ups, nobody. That's a career-ending mistake, no matter how unlikely it may be.
Not to mention that it's probably not a particularly popular decision amongst the public. Maybe it's security theatre, but people like it.