One key insight Jobs had was that as many functions as possible should be performed using iTunes on your computer rather than on the iPod.
As he later recalled: In order to make the iPod really easy to use
and this took a lot of arguing on my part -- we needed to limit what the device itself would do.
Instead we put that functionality in iTunes on the computer.
For example, we made it so you couldn't make playlists using the device.
You made playlists on iTunes, and then you synced with the device. That was controversial.
But what made the Rio and other devices so brain-dead was that they were complicated.
They had to do things like make playlists, because they weren't integrated with the jukebox software on your computer.
So by owning the iTunes software and the iPod device,
that allowed us to make the computer and the device work together,
and it allowed us to put the complexity in the right place.