Faxes kill trees. All that paper is a waste of natural resources. Score one for the tree huggers. Fax machines waste ink. Ink cartridges don't grow on trees either.
Fax machines are slow.
And with a fax, you still have to wait for a printout. Fax machines waste time. In the time that it takes you to go to a fax machine, retrieve a fax, and then fax or call in a response, you could have answered a dozen emails. Fax machines waste space. The machines themselves are a waste of valuable office real estate.