Because they aren’t allowed to, because it is considered a public service that should be equally available to all.
> If i live on a mountain top why should I expect people to haul shit to me for free?
Not for free. You pay taxes. And you should expect it because it’s what USPS does.
Now sure, there can be a whole debate about whether or not it should be the way it is, but that’s not what you asked. As per your original post:
> Unless they offer a better service than private industry, they will be a money sink.
It is a better service and it’s a money sink by design: it’s a public service that is funded by taxes. If they didn’t have insane pension obligations they’d be in a much better state financially, but they’ve been kept in a stranglehold over that for many years now: