There are plenty of businesses that become less relevant through no fault of their own (see 'buggy whip manufacturers'). That doesn't mean they require subsidies - it reminds me of Clevinger's father (?) in Catch-22 who made his fortune not growing parsley, investing government subsidies into buying more land on which to not grow parsley!

But the USPS is a good example of a point I've been lingering on since making my earlier comment - at what point does something become a basic right (or expectation, to prevent confusion with the Bill of Rights) in our society? Is postage a basic expectation? Is a home town newspaper a basic expectation? And if so, should we expect our taxes to subsidise them as we do with roads or healthcare?