It provides return to people who like it. It does not have to provide value to the "whole society" (which really mean, it does not provide a value to "me") to justify its existence.
I didn't say for the "whole society" but as a whole, i.e. if you sum up all the positives with the negatives. Heroin provides value for people who like it and somehow can use it without getting addicted. As a whole though I'd argue it's a net negative on society.
Casinos as-is don't need to be abolished, maybe their regulations need minor adjustment. I personally would abolish them, but it's low priority and not a hill I would die on.
But as far as the blockchain and gambling goes, that's not some silly vacation vice the guys go out to vegas for a few times a year/decade.
This stuff is advertised hard by influencers, misrepresented as investments, advertised at children, using foreign jurisdictions to be unaccountable.
It's not "it's bad because gambling bad".
It's bad because gambling is being forced shamelessly into the rest of the economy, often under false pretenses.