[Osmium]

You can blame the patent situation for this. There's too much risk for a big player (Microsoft, Apple) to bundle support for fringe codecs and container formats. VLC can get away with this because they're not a big enough target to be worth suing; they don't have enough money.

Sadly, it's also the patent situation that's responsible for the proliferation of codecs in the first place. Companies wouldn't feel the need to make their own (or their own custom containers) if they didn't have to worry about patent issues.