Why not ?

While I haven't looked at H.264 specifically many of the other MPEG pool patents have been
granted in Europe. 

Try getting the companies arguing against Theora to say that the encumbered formats are not
encumbered in Europe. Haha.

While software patents may not be directly enforceable in Europe, devices (including software)
implementing certain techniques can probably infringe.  Though this is outside of my scope of
expertise so I can't say much on that point. Whatever benefits the European system currently
has can not be guaranteed to last.

Beyond that, infringing US patents is unwise even if they can't be enforced in Europe... Since
a judgment against you in the US would be a problem if you ever need to do business in the US.
Perhaps this may not matter to a person, but single people aren't currently the subject of
patent litigation. Companies are, and this matters a lot.

This codec licensing stuff can largely be seen as a fight where there are a few LARGE and
deeply invested companies against a huge number of smaller companies.  The public suffers as a
result but they are just collateral damage.

This is nothing to do with what formats *can* be supported; any user is free to add extra
codecs to their browser. This is about what codecs will ship with browsers, and therefore what
codecs publishers can assume are present.

The question that needs to be asked is not whether Theora is better than H264, but is it
better than nothing? And the answer is clearly yes: it is quite a reasonable default to
provide to users. Those who pay for bandwidth, or have limited bandwidth, and can legally use
an H264 implementation can install one later if they wish.

Flash video sucks, but it is very widely used, just because it is convenient.  And because it
is widely used, publishers offer their video in that format. If publishers knew that Theora
would be available in their users browser, they would provide that format.