I'd guess it's because the tablets sell a LOT better in America than in Europe.

The American Amazon.com's sales chart has continually had the N800 or N810 in the top 5 or 10 for portable computers, whereas the European Amazon stores don't even have them in the top 1000. On the other hand, Nokia phones and smartphones sell much better in Europe than America. Same company, same products, but totally opposite sales patterns.

I think this shows a difference in markets, Europeans (and Asians, Africans etc) tend to go for things that look like phones whereas Americans tend to go for things that look like PDAs.

It's not just Nokia that has this difference, PDAs are virtually non-existent outside the American market because there's so little demand for such devices. Companies like Palm have virtually no presence outside America. I'd also guess that the iPhone (in its current form) will sell a lot better in America than elsewhere for similar reasons.

The tablets could be seen as Nokia's attempt to crack the American market, to complement their phones which sell well everywhere outside America.