Wi-Fi is flakey
I think people are failing to consider why Wi-Fi may not be supported yet.
Do we need a brief lesson in Wifi?
So the most common is 801.g 54Mb. That 54Mb isn't per connected device, it's shared across all connected devices. It's a half-duplex medium also meaning you can half that figure straight away. The highest rate any one device can achieve in the real world is around 20Mb. And that's assuming that Wifi is 100% clean and not also being shared with your Xbox, PC, Tablet, Smartphone etc for any serious use at the same time.
Now remember there are only 3 non-overlapping WiFi channels, yet in my street that are about 8 AP's in range. Every other AP on the same channel as mine eats into that shared 54mb of radio space even more. And that's without even considering high error correction overheads to co-exist in the same space as others.
Sure 20Mb is going to be fine for standard def streaming, but it's getting close for HD. WiFi is inherently an un-assured technology and subject to all kinds of operating conditions and interference.
It's well known that in the age of 40mb and 80Mb FTTC broadband, 802.1g 54Mb Wifi is now a bottleneck.
None of these issues occur on a 100Mb piece of Ethernet cable connected to a full duplex switch port.
Based on that, it occurs to me that YouView do not yet wish to risk having their brand tarnished by floods of support calls about chopping and buffering video etc because the end user has a poor WiFi setup. Even if they sent an engineer out to optimise everything, there is nothing to stop a neighbour standing up a new AP the very next day on the same channel wiping out that finely tuned setup.
As for Wireless N-150 or N-300 these are indeed a solution. Unfortunately for me I upgraded my router and several devices to Wireless N last year and for the life in me I cannot get anything to connect above 54Mb. I'm not sure if it's due to vendor mix of not quite standards compliant devices or that it's because I'm using the 2.4Ghz Wireless N so presumably there is simply not enough channel space left in there after all the other AP's in the neighbourhood have taken their slice.
Or, I as tried in vain to explain to my employer about 10 years ago when they started rolling out WiFi as some kind of utopia, you cannot guaranete thin air, and without very expensive tools you can't troubleshoot it either.