It may be because Apple's mission has been to design what they consider to be revolutionary products, not from a hardware specifications standpoint, but from a design and UX standpoint.
At least Steve Jobs' Apple did that with iPod, iPhone, and iPad and even the iMac to some degree. The Apple Watch may be viewed that way in a few years but it doesn't seem like it yet.
The problem with the watch is that it's in a space where its not clear there's any relevant need for that product to exist, commercially.
The MP3 player was the evolution of the CD player, which was the evolution of the walkman, which was the evolution of the boom box etc...going all the way back to minstrels. Music and its transportability have always been a big deal and improving that core function is a big deal.
The watch....time is important, but it is solved problem in that space, and it's not clear that it makes any thing else better (i.e. you implicitly need to use two-hands to control a watch interface, you can handle a phone with just 1).
At least Steve Jobs' Apple did that with iPod, iPhone, and iPad and even the iMac to some degree. The Apple Watch may be viewed that way in a few years but it doesn't seem like it yet.