It doesn't provide any value for society. Maybe a bit of entertainment, along with destroying some people's lives (problem gamblers). It basically just syphons away money from individuals to corporations while not providing much in return.
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.