It's not like they have a choice. Since MPEG-2 is covered by patents (which are underwritten by customs, police and eventually armies), they cannot really provide an MPEG-2 capable product without permission from the patent owners.
And those patent owners demand $2/chip or so; So RPi, instead of passing it on to all users, whether they need it or not, pass it through only to those who are interested. It's >5% of the cost for the Model B, and >8% of the cost of the Model A. I'm sure if they included it as part of the base, there would be people outraged that they did as well.
Despite the best intentions, limited resources and (despite what some people who have no experience with actually producing and selling hardware think) spectacular success - there will always be people who think they can do better. To those people I say: I'm here to cheer for you when you actually do. Until then, I will join Eben in ignoring you (or even Liz in mocking you silly)
It sucks a bit. I don't see it changing anytime soon. That's most of the reason I supported Parallela. That promises to be open, it probably won't be as much power as a nice GPU, but I want to compute with that hardware, and more problems will fit better. Plus I won't get trapped in some flawed API that has weird black boxes bugs and unpredictable performance issues.
They are optimizing for the British education market, not for some ideal libertarian education market in Somalia that can ignore patents.
And licensing agreements are a bitch. It might be against Broadcom's license with MPEG-LA to give enough info about implementing MPEG-2 regardless of jurisdiction.
Let them eat cake!