Because it's not true. The job of your Watch most likely will be a fancy new gadget to play with for a while. It is basically entertainment and fashion. But if the job to be done is to actually manage a To-Do list, there are better alternatives. Nothing beats paper and pencil.
That is your opinion rather than fact. It is true it will complement my iPhone. I get a lot of notifications often in situations that I don't want to grab out the iPhone. The Apple will simplify this.
I often miss calls in shoppping centres as the background noise is too much and the Watch will be a better notification system.
Also I play most of my music on shuffle - phone in the pocket all of the time. With the watch I can control the music.
It may not be the best todo list manager but it will do its job and a bunch of others. A pencil and paper are pretty useless at notifying me of a meeting location.