iPod Why can't iTunes/AppleTV/iPhone play most major formats?

[M. Malone]

So I get these AVI videos, then I have to convert them to MP4 video so they can play on my iTunes library/AppleTV/iPhone.

Can someone explain to me why doesn't Apple just open up their hardware to play everything? or at least the major formats?

Thanks to whoever will explain this

 

[NightStorm]

MP4 and AAC isn't a major format?

 

[M. Malone]

MP4 and AAC isn't a major format?

OTHER major formats, AVI, and whatever else