Agreed, it's one of those "be careful what you wish for" scenarios. A bunch of smaller retailers with disjointed UX and idiosyncratic service policies is the alternative to a giant monolith such as Amazon.
Lack of cooperation builds these monopolies like Google and Amazon.
If I recall correctly, US telcos couldn't even agree on which mobile payment system to use, because every company wanted to partner with someone and get a larger piece of the pie. Now it seems the only mobile payment system anyone actually uses is Apple Pay.
That anecdote aside, I agree it would be awesome if such a standard existed. I just don't see it working out since retail is such a cut throat business and everyone will be looking to undercut their competitors.
Remember, competition is good for the consumer and bad for companies.