The whole reason is obvious. The House and Senate have abdicated much of their traditional responsibility of passing legislation that matters and instead letting lawasuits work their way up the chain of the Federal court system to be coded into law by decision not statute.
That way they can straddle the fence, lie, hem and haw and blame someone else. Fundraise ad nauseum from “unelected officials” being faceless evil.
The other component is letting unknown, unelected, permanent bureaucrats in the alphabet agencies make up rules as they go and stretching the boundaries of any existing statue or law. They’re never called on it, never held accountable and can’t be fired.
So there you go, lazy legislature, too powerful court.
You are correct. Legislation by decree.