People do all sorts of freaky things in the name of entertainment all of the time and they do it for what? That's right, profit!
Not in cities/states where the majority has decided a particular flavor of freaky is unacceptable. Not legally.
Noone is forced to work at a bar! You couldn't pay me enough to be a window washer. People choose to do that for money. You couldn't pay me enough to go out on a lobster boat. People do that for money.
Those things are currently not harmful to other people by their very nature, are they? More to the point, those things are not currently under public scrutiny.
(And you wouldn't wash windows to feed your family if it was the only job you could find? Really?)
At one time in this country, prostitution and gambling were easy to find, and not illegal.
Why did that change? Did the big bad government come in and put those brothel owners out of business?
Yes, if you want to look at it that way. They did.
But what led to them closing? The citizens, the voters, decided those things were no longer socially acceptable. It no longer fit the societal norms of the majority. The citizens demanded government act on their behalf and get rid of such establishments.
My point is, smoking is going down the same road. Is it harmful? Yes, but even that takes second seat to the changing social norms of the country.
The gov, under public pressure, is responding to smoking much the same way it has done to other once socially acceptable practices, which have for whatever reason, fallen out of that acceptable zone.