USPS to return to its core competency of delivering addressed letters and small packages rather than handling general freight
Mail isn't freight and the bill of lading does not really belong at the post office
It's a legal issue where no consignment or bailment is created on any legal description of goods and valuables at the time and place of mailing a package.
Customs and import duties are not legally due on small items mailed internationally either, for which reason the "gift" box is traditionally checked as a silent protest. Mailed items are packaged and sealed as "diplomatic pouches" and deemed concealed and should not be opened or inspected without a warrant. Post offices should respect customers' privacy and not be burdened with heavy freight.
What value should be declared on the mailed items and possibly reimbursed in case of loss does not and cannot depend on the actual contents of a package, only on whether or not it was delivered intact.

Freight isn't really "mail"

“The USPS is a longstanding and trusted partner and we remain committed to working together,” Amazon spokesperson Steve Kelly said in a statement, adding that the company is discussing “ways to extend our partnership.” ¶But Kelly said Amazon was “surprised to hear” the USPS wants to “run an auction” for some of its shipping capacity.
We're not kids here, and we're seeing a "pattern and practice" where mailed packages are routinely being damaged by rough handling, falsely warranted for inspection on sloppy police procedures, "accidentally" opened up, seized, confiscated, forfeited and auctioned off wholesale by "the feds," either in their official capacity or as a "side gig" for federal cops or postal workers.
That is the vice of using a mail and package service for general freight without a legally enforceable consignment of goods or a valid bill of lading including a legal description of the valuables shipped.

