The USPS is actually in the very unenviable position of being required to lose money to subsidize the rest of the Federal Govt. Several examples:
Congress sets the amount of money that the USPS has to pay into its pension and healthcare funds. This money is "held is trust" by congress (i.e. was spent 5 years before it came in.). The USPS has been forced to over pay for pension and retiree healthcare costs by over $80,000,000,000.00. Most of the $7,000,000,000.00 loss this year comes from an $5,000,000,000.000 payment into the retiree health benefits fund. In fact the USPS would have been profitable in the last 8 out of 10 years if it wasn't forced to subsidize congress's spending binges.
Congress requires the USPS to give rates to Non-profits that are below cost. Theoretically, congress is supposed to pay the difference, but hasn't for 17 years.
Periodicals (Time, WSJ, People ect) get preferential rates because of the lobbying power of the press. If I mail a 2.1 oz flat at presort standard rates (after putting the data through the national change of address database, something not required of periodicals) the lowest rate I could possible get is $0.194 per piece. I only get that rate if I bring it to the Sectional Center Facility where the mail will be sorted, and I presort it to the sequence the carrier walks in, and have pieces going to 90% of the residents on the route. That same piece going periodical rate only pays $0.16 for faster service.
I'm not denying that the USPS has problems of its own making it needs to deal with. It caved to the unions far to much in the past, giving it a very expensive workforce that thinks it constantly battling the evil management.
All of this comes from many years in the mail service provider industry. I'm not Aunt Edna that mails 3 birthday cards a year, and thinks that entitles her to complain that the Post Office in town is closing, even though it is within 2 miles of other Post Offices. I do multi-million dollar postage amounts every year. I am on first name basis with several USPS VPs.