There's rules and regulations against it, for one. Should locals be allowed to do whatever they want on their property with no regards to how it will impact neighbours and local economy? There's a reason we have zoning laws, etc, in place. There's lots of things we stop locals from doing because it's for the better of the community as a whole, and renting out short-term to tourists should be one (and, again, it sometimes already is but AirBnB allows them to skirt the regulations).
Locals should absolutely have the right and power to change their local laws to prohibit Airbnb. However, I'm not going to feel guilty for using Airbnb in places where it's legal, because it's simply a better product than hotels by a long shot (when it works).
I'd be willing to bet that in most places they're not legal, there's just nobody enforcing it. They're willfully in violation of a lot of rules and regulations that are already in place. And harming the locals so entitled tourists can think they're at home.
