For years, we had mail misdirected on a regular basis by USPS. It would not be an exaggeration to say at least once a week we got mail for other people. You can pretty much guess if that is happening often, your mail is probably also being delivered incorrectly. We tried complaining to the postmaster, but the reply we got was that the gentleman was only a couple of years from retirement, that he was only staying long enough to get dental work done that was covered by insurance while he was still employed, and that it would be close to impossible for them to let him go. It was almost a joke - we are in the country, so the territory was fairly large - but everyone knew about it and just kind of shook their heads.
Still, all of us make mistakes, and no delivery service is going to be perfect. I wouldn't think of shipping anything of value - monetary or sentimental - via any service without insuring it. The additional cost is minimal.