What's the deal with trying so hard to defend the advertising of an objectively harmful industry?

I think a good parallel here is Tobacco advertising. Smoking is harmful in every way, therefore I don't see any reason why advertising it to a broad audience (which will inadvertently also include children) is something we should allow.

What's the net benefit of allowing such advertising? I don't see it. Yo could argue something about rights to free speech or some variation, but societies still have a responsibility to look out for the health of their people, no?