Given that they mention "$16bn" repeatedly, it seems pretty clear to me that their comments are regarding marketing mail specifically, not the full set of services USPS provides.

I feel quite comfortable saying that there has been zero value to myself, or any other human, in delivering marketing mail to my home. I never look at it, I never read it, it just goes straight into my recycling as soon as I identify that a letter I've received is not from someone I have a legitimate personal or business relationship with. I have never made any purchase as a result of receiving an advertisement delivered to my home by USPS.