You're title and reasoning doesn't match. The reason people think it is an accessory is because of the name and the look. Even those interested in getting it will find out it is more expensive and not what they originally wanted to buy so not every one of them will want the actual device due to price or not knowing the deal of buying a next gen console. Those who think it is an accessory see it as optional and don't realize their system is not being supported any longer and moving into the next generation or don't care.
How wouldn't this be a problem? Sure there are other issues, but this is still one of them. The casual market is not a very informed consumer base and Nintendo has not made it easy for them to know what their product is. If they called it the Super Wii or the Wii 2 thing would have been more apparent. Now they just need marketing, like they did with the 3DS saying it wasn't a DS. They could easily start marketing the Wii U as "The New Wii" and the public would understand easily as that has been effective with Apple, even though their use of a numbering system works just fine so did "The New iPad"
Before the PS3 everyone was nice to me :(
