Yeah? I'd love to hear why.
You seem to live in a world where everyone owns only Apple products.
This word does not actually exist.
There are numerous appliances which will not read various formats, including products which will not read mp4. Not many, but some I've come across do not.
Plus while experimenting with a wireless media network I've found that mp4 files do not come across as well on a television set when streaming from a central hub. Avi files generally look better with my current media set up, for example.
If it has been ripped especailly for ipod playback the resolution and framerate may not be of a high enough standard for young brittonware.
Alternatively they may, as someone I know has done, decided to go into bed with Microsoft and have their media set up based on their various formats. Obviously in that case a 'ipod version' would be no good to them.
Or of course they want a 'non-ipod version' to watch either through a network on thier televsion or on their PC monitor which they can then convert themselves to an 'ipod version' should they feel the need to have it on their ipod - should they infact own one. Personally I store my media files in the avi format, and only convert to an ipod combatible format when I specificaly wish to have a copy on my ipod for a train journey or some other activity away from the home.
I could continue as to why it's a stupid question, but I have better thing to do this evening.
