Why does the Postal Service offer flat-rate Priority Mail shipping? Doesn't it lose money?

The US Postal Service offers Domestic and International flat-rate Priority Mail shipping envelopes and boxes. Shipping something heavy from Alaska to Florida would seem to cost a lot more than $8.95. People use this service to save money. In addition, the USPS has to provide the boxes and envelopes. How can this be a good deal for the USPS?Why does the Postal Service offer flat-rate Priority Mail shipping? Doesn't it lose money?
Contrary to the above answer...

the USPS is required by law to break even, that is neither make or lose money. If the USPS was privatized it would spell disaster for the average American. No private company would be willing to deliver 6 days a week, let alone to most rural areas of the country. If you look at countries that have privatized some mail services, the private companies skim off the high profit large city mail delivery, while leaving the government to deliver to all of the high cost small town and rural stops.

Indeed some people use flat rate Priority Boxes with a heavy weight, others with a light weight item inside. Most Priority Rate parcels are less than 5 pounds in weight and because of the large volume it is beneficial to both the mailer and USPS.Why does the Postal Service offer flat-rate Priority Mail shipping? Doesn't it lose money?
the answer lies in volume and also distribution of cost and revenue. if it looses on some, it gains on some. also, it is a govt. department for the benefit of citizens.Why does the Postal Service offer flat-rate Priority Mail shipping? Doesn't it lose money?
If you look at the USPS more closely, you'll see that it doesn't make much money at all. In fact, it loses money every year. It's terribly inefficient, most likely because it is government owned and operated. It would work better for everyone if it was privatized.
They do? I sent 2 parcels last December from Pittsburgh to NZ and it cost me over US$100