Cartographers would be limiting access to their maps by choosing this medium and this would be unethical. The same, of course, can be said for maps on paper. They also can not be as easily duplicated or transported as maps through the Internet. The printing maps on paper can only be justified if the intention is to limit their distribution. From this perspective, the printing of maps on paper is unethical.
Economic considerations are, of course, important.
Cartographers must earn a living and paper is a tangible medium that can be exchanged for money. The maps are printed at a larger size and a finer resolution so that they cannot be easily duplicated. The paper medium forces to map user to pay. But, maps should be viewed as something more than an economic commodity. They are like a window to the world.