Amazon eBook questions that are rarely asked

Why are Amazon ebook reviews from US readers more important than reviews from international readers?

Have you noticed that reviews from Amazon.com are aggregated across all other international Amazon sites, but that the reverse is not true? If someone kindly posts a review of a book on Amazon.co.uk, it is stuck there, and not aggregated to Amazon.com. Why? Is a UK review less valuable than a US review? Are reviews from Canadians, Australians or India inferior to US reviews?

Source here, via Sofia Tania.