I understand why you say it’s an environmental waste, and that has some merit, until we consider the impact of junk mail, flyers, etc. There are many areas of modern society we can economize and improve upon before we get to the impact from paper billing.
What is your alternative to a pile of paper on a desk? It needs to be persistent, timely, and reliable. Online billing portals mean I need to log in on a regular basis to multiple portals in order to check for notifications and invoices, which simply doesn’t work for my brain. Having a bill sitting out, on which I am able to write the payment amount and date, permits me to keep track of the bill throughout its lifecycle at a glance from across the room.