What your saying I agree with, the United States Postal Service make mistakes, it don't alway don't get Priority Mail Delievered in the projected 2 - 3 days.
Most of the time the Many Millions of packages, letters, etc, get delivered as projected. Sometimes something is lost, destroyed, or delayed.
Most of the time USPS is better then UPS, FEDX, or other carriers. Having actually had something lost byUPS, and another item destroyed by FEDX Ground. Both case were nightmares to get claims settled.
One of my rules in never mail anything important right before Christmas, as all the carrier are work at MAXIUM capacity plus.
Dont forget, its maximum theft season too
Anything stolen at Christmas time(all of Dec) should be mandatory 1 year minimum in PRISON, no matter your age.
Should apply to the rest of the year too, but it's a start.