I think part of the reason for commemorative stamps is that they're profitable. Collecters buy them, but don't use them. If there were no commemorative stamps, this additional market would disappear, and postal rates would be even higher.
So if postal rates could be reduced by having the USPS run whore-houses out of the back of Post Offices, should they do that? I mean, if they didn't, postal rates would be even higher, wouldn't they?
The government should make it's money through taxation. If you want them to make money in other ways, be prepared to accept them doing all sorts of foolish things in pursuit of a buck.