Boxee, Google TV, and such are able to license Netflix and use their technology because it's much harder to hack them. Netflix has been fighting movie companies for years now to get full Linux support because Silverlight is the only player technology with the DRM to satisfy the studios that movies can't be copied from the stream, and Microsoft obviously has no intention of making it available on mainstream Linux distributions.
I believe that Boxee, Google TV, and 360/PS3 all use other technologies, but that can be inherently less secure because it's harder to get inside of them. Also, they can afford to pay the monstrous fees to work with Netflix and develop a solution that will satisfy all of Netflix's backers.
Licensing technology, especially with all of the patent stuff that's been going on lately, is an incredible undertaking and costs a lot of money, and many companies are unwilling to license to companies like Canonical because Linux is a huge administrative headache due to its openness and peoples' desire to have open systems.
At least, that's how I understand all of this. I could be wrong.
Secondly, how would they license? Most of the code they could license requires a charge per copy. RedHat , Ubuntu and most Linux distros encourage the free redistribution of their disks. You can download it for free(aside from bandwidth charges which RedHat is not involved with. They don't even know how many copies are really in use. So, either they would have to change their whole distribution model or they would have to pay for something that is fairly nebulous. Fluendo has published a version of the MP3 codec that can be distributed for free. They purchased a license that has no per copy costs, but that is unusual to even have that as an option.
Finally, the RedHat company produces the RedHat distro for commercial use and the Fedora distro for home use. There is an active community of Fedora users who happily use it after 5 PM and you can find how to get most codecs working in Fedora, if you search a bit. The freedoms associated with Linux make it much more pleasant to use that any proprietary solution available today. I would also say Linux is more powerful and easy to use, but I can see how not everyone would agree about those, since your experience and workflows can drive those comparisons. OpenSolaris was making good progress. It is a shame it was killed a little before it got to the point where it was usable for everyday duty for the average person.
The desktop distro teams can't organize enough to get support from major companies, and the enterprise companies can't push into desktop because it's financial suicide to try and support normal desktop users who can barely use Windows.
Talk to companies like Broadcom or AMD / NVIDIA about making their components work much better with Linux, first. A lot of the issue is on their end, with not providing interfaces and drivers for distros to include.
Canonical, Novell, and everyone else try their best to include what they can for their distros but it's hard when the companies making these computers don't help much.