When the private sector or persons build their own recreational areas, they can decide the rules for them.
I'm all for Liberalism and one's right to decide for oneself, but I also believe that smoking needs to be fought at every step. The smoking ban has been so great in my country, I truly applaud it.
EDIT
I'm not trying to start an argument, as I hardly realise the situation in NYC (compared to where I live etc). But this is public responsibility too. If individuals were able to keep the park clean by not littering, throwing cigarette butts around and all that stuff, this law wouldn't be there.
We have a law against drinking alcohol in public, in public parks as well. But in Summer time, the police don't bother anyone who take it easy and enjoy a couple of cans/bottles. If you get rowdy or loud though, they'll come fine you.
Just don't forget that the public has a responsibility too. It's not always about the crazy government trying to shackle the little man.
This is intended as participation in polite discussion please, take it in that light.
First, the private sector has built recreation arias for adults in the form of pubs, neighborhood bars, and rest arias both in privately owned offices and gardens for the use of a business' employees. The public has taken them away a long time ago. I agree that one shouldn't leave their cigarette buts laying around, but that does happen when you remove the ashtrays and smoker friendly areas. You can't remove reasonable privately owned access and public sanitation and then say that one should avail themselves to private arias and not be so messy.