WebM is a relatively new entrant into the encoding field, Only getting opened up in the last 8 months. Ogg has always been a fairly significantly worse codec then H264. "Even the 1mbps Ogg Theora clips are not on par with the 468 kbps h264 clips."[1]
Considering that MS and Apple have been working in video for a long time now they chose the codec with the best available experience for their users (who aren't the ones picking up the licensing fees).
Instead of embracing the patent encumbered codec we should be thankful for Google to actually buy a codec (VP8) and release it _for free_. I couldn't imagine this from any other company.
Still many people just want their h.264 no matter what. It's bad for a free and open internet, that's my belief.
Considering that MS and Apple have been working in video for a long time now they chose the codec with the best available experience for their users (who aren't the ones picking up the licensing fees).
[1] http://arstechnica.com/open-source/news/2010/02/ogg-theora-v...