Pigovian taxes are supposed to be a "less inefficient" and more practically viable way of dealing with externalities, compared to cruder forms of central planning. Of course it's been quite easy to simply proclaim externalities everywhere--and even to help bring about their presence by making the "public sphere" bloated rather than trying to privatize it in a more straightforward way than Pigovian taxes.

Little wonder that people seem to use "Pigovian" to refer to every bit of nanny-state paternalism they see. There's even some precedent to this. In addition to pollution Pigou himself suggested that alcohol be taxed to control its alleged externalities. Of course now we often barely even reach for that fig leaf for much of what we call "Pigovian" in the brazenly looser sense.