Except for most people a watch is fashion, not a tool. A phone is a tool, and you expect it to perform certain tasks that make your life easier. A smart phone is objectively superior at those things, thus you want a smart phone over a dumb phone.
A watch, on the other hand, is much more a fashion statement and status symbol than a tool. A $10k Rolex doesn't really keep time any better than a $20 Timex, but that's not why one buys the Rolex. Most teenagers _stopped wearing watches_ over the past decade or so because they use their phones to check the time, it's only when we've started dressing more professionally that we've started buying watches.
I don't buy wearable tech as the next big thing in hardware. I don't think most consumers will pay $500 to have something on their wrist that does a fraction of what the thing in their pocket does while looking worse than the "dumb watch" it replaced.