All the competitors did the same thing. I'm not even sure what "adding music" without a computer would look like. Apple just streamlined and simplified it by assuming you'd use their products from end to end (iPod - Mac - iTunes).

That means removing features from the device was balanced by adding them to another Apple product i.e. it wasn't orthogonal at all, it was part of the digital hub strategy that could be considered to be holding them back now.