I agree, existence must imply the program being mandatory, for exactly the reasons you describe. But perhaps the fact that the justices nearly-unanimously agree

I agree, existence must imply the program being mandatory, for exactly the reasons you describe. But perhaps the fact that the justices nearly-unanimously agreed on its unconstitionality means it should not have existed? You have to argue the legality of the program on the merits, not on the basis of "well, if we didn't violate the constitution, the program would not work". And yeah, I am not trying to pass judgement using the label of socialism, I am trying to draw parallels to what people often decry as one of the evils of socialist states. I understand that these programs were not created in such a context; I certainly do not care about party affiliations or political leanings, only the direct, observable outcomes of the program.