The postal service is a vital part of commerce. Consider how much sorting, transfer and transportation is needed to pick up that one birthday card and take it across the country (or the world) and deliver it within a few days.
Compare that to a cab ride or any other delivery service - if there were no USPS. The cost of a stamp in the private sector would approach $2 per letter.
Certainly, improvements are needed in management of resources and cost containment - but this is a Government subsidized enterprise. No profit motive = no incentive. No surprise.
If USPS could eliminate the problems inherent in being the biggest subsidizer of the US government, your mail service would probably change.