Nintendo does enjoy going after your wallet, and they're not shy about it.
Remember Final Fantasy: Crystal Chronicles?
It's a GameCube game, but if you want to get the most out of it, such as effective inventory management and special minigames, you need to have a Nintendo GBA and a link cable.
Oh, and it's a co-op game, so you're barely getting anything out of it unless you play with your friends. Each one of your friends needs a Nintendo GBA and link cable as well.
Oh, and if you want to get the most most out of it, you'll need to buy the Nintendo e-Card Reader [http://en.wikipedia.org/wiki/Nintendo_e-Reader] and collectible trading cards to swipe.
By the time you have the necessary hardware for a four player game (assuming you already had a Gamecube and standard controllers) you've paid over $500 ($100 per GBA, $20 per link cable, ?$ for e-Reader, ?$ for cards, ect).
Though Crystal Chronicles took it to new levels, this was not an usual trend, and similar features could be found in Zelda: Wind Waker, Pokemon Colosseum, Animal Crossing, ect.
They toned it down a little in that the Wireless DS requires no link cable (and not that many Wii games make use of the Wireless DS, if any) but haven't knocked it off. What do you think all those weird accessories [http://cache.gizmodo.com/assets/resources/2008/01/18in1.jpg] for the Wiimote are for? At the very least, you've probably got numchucks, and a lot of the downloadable games require you purchase vintage controllers (if you don't have one).