I don't fully agree. I do think it's a pretty bad and predatory industry but there's a tiny bit of value.

It does provide good estimators of probabilities of real world events. Like if someone would ask me how likely it is that team X will win the world cup I'd look up the betting odds. In general, if there's a betting market for something I'd always use the odds as placeholder until I can come up with a better estimate (which quite frankly seems unlikely). If I were to build an ML model that tries to predict something with a betting market that would be the baseline I'd measure against for example.