Just because a particular market is free doesn't mean it's useful to society at large.
If it's not useful to society, society has no moral reason to tolerate it. If it indeed benefits a few individuals massively while on net reducing utility to society, an argument can be made that society has a moral imperative to ban it. Hence the limitations on gambling, on alcohol and tobacco marketing/sales, etc.
If it's not useful to society, society has no moral reason to tolerate it. If it indeed benefits a few individuals massively while on net reducing utility to society, an argument can be made that society has a moral imperative to ban it. Hence the limitations on gambling, on alcohol and tobacco marketing/sales, etc.