You make some great points, although I must disagree that the duplication of functions are made by design. Perhaps Apple is spinning it this way on their marketing pieces. The "Start on Apple Watch. Continue on iPhone." kind of proves that. They will not flat out say the battery suck or that doing too much on the Watch is not feasible due to battery or small screen. They would never say most of the features require the IPhone to work. Cuz at the end of the day, the IPhone can perform more than the Watch, minus the shared drawing or heartbeat from the Watch. I see the codependency of the Watch a big negative instead of a selling point, imo. That is also true for all the makers, not just Apple.
When I tell friends about smartwatches, they say, "what can't I do on my phone that a smartwatch can?" Then of course we also have, "why would I want a smartwatch when it requires me to take out my phone anyway?" If makers can satisfy these 2 questions, perhaps the general public would view smartwatches more compelling? IMO.
For some of us, we can afford it, the Watch looks cool, and the conveniences could be helpful.