Video encoding is a lot more complex and specialist than audio encoding as well, which is another reason you might want to find your own tools to do the encoding. Also while PCM WAV is a de-facto standard for uncompressed audio, I'm not aware that there's an equivalent for video. Uncompressed files are so huge that I think everyone mainly deals in compressed formats (perhaps at very high quality settings). So while audio typically involves just encoding, video could involve transcoding, which is more complicated and lossy. Throw patent-encumbered formats in to the mix, and the fact Windows doesn't have a built-in video encoder like it has for audio, and a wide range of exotic formats across platforms, and you find it's a real minefield. That's why it's not supported the same as with audio.