USPS is a federal agency. Their objective is to deliver your mail.
Note that I said “most”, not all. There certainly are notable exceptions to the rule but I can assure you that most agencies have a ‘protect the kingdom at all cost” mentality. Their jobs and positions are paramount and so they have a voracious appetite for money to fund their endless stream of programs. What else would most of the paper pushers and bureaucrats do for a living?