Right now it seems as if the Wii U's biggest issue is that it doesn't have any Nintendo system sellers yet, or at least not a sufficient number for somebody to buy it if they're on a tight budget. I personally have yet to buy a Wii U, because money is quite tight and I'm waiting until I'm "forced" to (enough Nintendo games are out for me to buy one.) I was thinking: how popular are Nintendo games? Does their popularity fluctuate? If so, can the popularity of Nintendo games decrease with less exposure? But that wouldn't happen with the existence of the 3DS and the exposure it gives Nintendo franchises through its larger base and high quality releases. If there are people who like these franchises on the 3DS, certainly they'll buy a Wii U as well, eventually. So the logical conclusion is that it is inevitable that with more games Wii U's sales will pick up, not just moderately, but significantly because it makes the fans of these franchises less resistant to buying a brand new console knowing that not only one of their favorite games is on the console, but multiple games they enjoyed very much on the 3DS (or priorly) can be found on the Wii U.
So all in all, by supporting the 3DS, Nintendo is maintaining its [Nintendo's] significance for when the Wii U is buyable [to those who are more conservative with their spending.] If they didn't support the 3DS as they are, the franchises might lose their word-of-mouth and significance in modern memory when they are actually released on the Wii U, and this would be quite devastating on all ends, with a weaker 3DS and a perpetually weak Wii U.
Overall, the 3DS and Wii U support one another, and boost eachother's sales because they have slightly different audiences who enjoy the same franchises.
P.S This thread was partly for those of you who think of the 3DS as a parasite of the Wii U by taking Nintendo's time and resources.
