Wishing away

Whilst the new Amazon design is very fancy and navigation is supposedly easier, there seems to be an elemental problem.

Being from the UK, I signed up ages and ages ago, via the .co.uk side of Amazon. Today, I accidentally logged in via the .com domain. For a moment, I thought the stupid site had lost my wish list. But the truth is, it doesn’t seem to be able to access it across stores.

So, here is my question. Why can I log in to any Amazon shop regardless of country, but not access information I have stored there?