On the Wii U I don't see that much of a point, however on the 3DS you're right especially considering the 3D possibilities. I guess they just want to avoid people pirating movies or something, I don't know but it's something a lot of people would like at least.
On the Wii U side of things it's an opportunity gone to waste I agree, but allowing your device to play media formats is also something that costs time and money, I'm not saying that there aren't people that want that, I'm saying that they have a reason not to looking at the business side of things.
The "itunes" idea however should totally be implemented however, as it's something most people would want. Taking those babysteps I hope this is the direction they're heading, lets see how things evolves, going from Wii to Wii U was a giant leap, we'll see if they have what it takes from here on.