positive externalities are charities, or non-profits at least.
There are zero private businesses which generate positive externalities that they do not charge money for (and if they did, then it's no longer an externality). To do so would mean they leave money on the table! They can only shed negative externalities.
There are zero private businesses which generate positive externalities that they do not charge money for (and if they did, then it's no longer an externality). To do so would mean they leave money on the table! They can only shed negative externalities.