That is such a copout reason to not give paper copies, the real reason being administrative assistant laziness. In this day in age, electronic copies are expected, but not providing copies to students often means they will just go ahead and print it off themselves anyway, defeating the purpose of such policies.
It is easy enough to use recycled paper (and to request that waste paper be recycled). The footprint of that is rather negligible and if it improves the educational experience to have paper copies of lecture notes, then its wise to keep those. It is amazing how relatively minor binge uses of paper like this are cited as "killing all the trees" when the medical system in America is a mess of overuse of paper products. Move to electronic medical records before scrimping on educational uses of paper.