Well, what you say is true, but the truth of the matter is a lot of people don't find pressing the power or home button on a phone a big problem, as evidenced by the huge decline in watch-wearing consumers. I certainly don't mind that. EVERYONE I knew used to wear a watch, but I'd be surprised if it was even 25% of my friends and family do now.
I'm guessing it is because you don't have to remember to bring a watch, and you don't have to spend money to buy a watch. And for mechanical watches it also means you don't have to adjust the date or the time. In that context, I personally find having only the smartphone more convenient than have both a phone and a watch.
What's also telling from your comment is that it sounds like you'd also think Smart watches suck, at least as currently implemented. You want something extremely convenient and out of the way, that you just glance down quickly to see the time and date. That is not the purpose and design of a smart watch in 2013.
Beleive me! Wearing a proper watch can not only make you look good. But, it might be the difference between looking professional/serious and looking causal or non serious. These are stubble things that can add up to make the big impression when you are out to get client etc.
I have seen people peeking other places for a quick view of time when they are doing something or waiting for someone even when they have a mobile phone in there pant pocket/ purse. There is nothing like having a watch whenever you are driving/commuting through the public transport.
Tablets were termed useless when they were first released by Apple in the era when desktops and laptops ruled the roost. But, now tablets have created a whole new market for themselves. And people who thought them to be useless realized after using them that they are actually convenient and fulfilled a need that they never thought existed.
My point is smart watches are here to fill a gap that people don't know exists. But, once you would use it then only you would realize what was missing till now. I can easily predict that just like the tablets smart watches too would become a necessity and people who don't wear watches till now. Would actually start wearing them.
Smart watches are not only going to be smaller and thinner. But, they are going to be the jack of all trades. While looking ultra cool and sexy. I know that bands can be changed to different colors even now. And watches are looking like the expensive black Rado's which give the watch a monochrome look.
Screen size doesn't really restrict its capability. Because you are not going to watch movies on your watch. Vibration, light,sound,voice etc are some of the many ways that can be used to process/recieve info through and from the watch even without the use/need of a big screen.