The government controls countless aspects of what the owners of private property can and cannot do.
For example:
A bar owner cannot sell beer to 12 year old kids.
A store owner cannot sell cigarettes to children under 18.
An apartment owner cannot deny leasing to a minority.
A restaurant owner cannot serve meat that is not inspected.
A day care center owner cannot store toxic waste at the day care center.
A bar owner cannot pump toxic air into his bar.
Each of the above government regulations are instituted to protect the public safety or at least the perceived public safety. Thus as long as their is a perceived public safety threat from ETS there will continue to be smoking bans.
The stark reality is that within 10 years there will no be a jurisdiction in the U.S. where there are not smoking bans.