"...even a quality service may become obsolete"

That's not without merit. Consider the flint knappers who made those stellar Clovis-era spearheads; buggie-whip makers who produced a truly excellent product; and the drovers who herded range cattle to the railheads to be fattened into prime beef in the feed lots.

OTOH, friends sent me a book, recently. I think the process there presents a minor (call it 'trivial' if you like) instance for the proposition that the USPS is NOT "obsolete." Without USPS and its bookrates, it probably would have been delivered by (UPS|FedEx|pick your poison) on Monday, rather than Saturday (and, I believe, at a higher cost to my friend).

Or, the friends probably could have found an e-book version... and sent it electronically. But in that case, I probably would have received an email, rather than physical evidence of the thought and care that went into selecting the book and the gracious, handwritten inscription inside the front cover.

One can, of course, hold that this very personal appreciation fails to present a case for continuing USPS existence.

One can also argue that the effective demise of the railroads' passenger service reflected in some large measure, the then new popular mindset that being 'an American' entitled you to a car, an uncrowded highway, and a parking space near your office.

There is, of course, some merit to that view. But, we know how long and how well that worked... and how high the cost of subsidizing that mindset, today.

But terminating most passenger service also had the effect of reducing traffic on many branch lines contributing to the abandonment of freight on those as well. And the consequence?

Tractor-trailers (operating with effective subsidies that make those provided the railroads fade as a bete noir) beating secondary roads to death and clogging the same Interstates that -- initially -- provided some minimal justification for that "uncrowded highway" hope.

And, finally, an argument that I can't square with my semi-Libertarian economic views: If USPS goes away, will competition among the alternatve providers actually enhance service and drive down prices?

Sometimes it does; sometimes it doesn't, but I certainly haven't see much evidence that we can count on it. Thus, I respectfully disagree with the Tea Party/Libertarian/radical GOP inclination to believe that the proposition "smaller government is better government" is globally true.

IMO, t'ain't so.

Nor do I think you've presented a compelling case for the judgment "there's really no reason to have a USPS anymore."