That's the only explanation. The phone company wants every tree dead. Below is a photo of all of the phone books that have been delivered to my home this year. I've added the Mountain Dew can for scale... and because I like Mountain Dew.
The real tragedy of the phone company mowing down our the forest is that it is pointless. Having received these 10 phone books, how many do you think I'll use? One? Two perhaps? Nope. The answer is zero.
Not one of these phone books will get put to their intended use. Why? Since you're reading this, you likely know what I'm going to say. The reason these won't get opened is that they have been replaced by the Internet. Anyone with a network connection can instantly locate information far more plentiful and up to date than all 10 of these books combined contain.
Luckily, they at least make good targets.