One component of this seems to be that by moving online we've lost access to the labels on goods. In a store, you can usually just look at the "made in <X>" label printed on the box. On amazon, that information is pretty much never available.
Possibly this is partially because they're commingling inventory made in different places, but I think a lot of it's just that amazon doesn't see any reason to force people to list that.
I once asked a person working on a large music instrument website why products "Made in USA" or "Made in [European Country]" were labeled as such, but the ones made in other countries aren't, and the answer was pretty simple: they A/B tested it, but "Made in China" or even "Made in [Asian Country]" drives people away. Japan and Korea have a good reputation for instruments, though.
Possibly this is partially because they're commingling inventory made in different places, but I think a lot of it's just that amazon doesn't see any reason to force people to list that.