I know for a fact that aerospace, electrical, and mechanical engineers working on designing rockets, nuclear reactors, space capsules, and electric charging infrastructure do not need this credential. And so most of them do not have it.
I'm not sure ABET is the most relevant here? What would making CS programs accredited change?
And you didn't quite mix it up, a degree from an ABET accredited school is required to get your professional engineering certification, which is often required in cases where engineering designs carry legal liability.
I am unable to find concrete numbers on this, but I would bet that the majority of employed engineers in the US do not carry a professional engineering certification.
My point is that accreditation boards and trade unions can help set standard minimums of what an engineer (or trades person) will know going into a job. Of course employers can ignore them, but in general those standards help bring consistent expectations to a given trade.