“What’s the rationale for legalized sports betting [that mirrors the rationales for these other two decisions that you are placing in the same category]?”
“Just make money” or “the Romans did it” are unlikely to fit the bill.
Sounds more like you're wanting to ask a more generic question on why addict gambles, but if you want to understand the rational of an addict, then get in line. The only thing to understand is trying chase the high in whatever form it takes. Ask an addict and they will tell you there's no explaining it.
To me, the "HN fasion" is not accepting that there are things that exist that are not rational and no matter how much you want to logic your way to an answer, it will never happen.
This is about policy errors and the degree to which those errors are unforced.
The question is whether sports gambling was just as “forced” as the surveillance state or as deindustrialization.