Just like a tablet, a desktop PC, or a dedicated video game handheld, it just depends on your personal situation.
My personal situation:
- I drive about 50 minutes on average to and from work everyday. Because of this, I tend to listen to podcasts through my phone mounted on my dash. If I want to pause it, change the volume, etc I need to reach over and awkwardly try to unlock and navigate my screen while driving on the highway. With a smartwatch, I could just do that from my wrist.
- I'm playing music and want to change the track? Ditto.
- My girlfriend texts me while I'm driving? I can just glance and respond to it with voice from my wrist.
- I need to change my map navigation (I use GPS a LOT) or stop it? Seeing the pattern?
- I'm using GPS for walking directions. Instead of having to hold my phone out in front of me, I can just glance at my watch, or even better with the haptic feedback, it just buzzes me in the right direction.
- At work, I tend to leave my phone on my desk because I get a lot of notifications and emails during the day. With a smartwatch on I can just leave the phone in my pocket, and glance at my wrist any time I get a notification as opposed to pulling out every time it buzzes and I'll never forget to leave my phone lying there.
- My girlfriend leaves her phone lying everywhere because she'll otherwise miss any notification or even the phone ringing with it buried in her purse. She has lost two phones this way. With a smartwatch she can leave it in her purse a lot more.
- I'm playing a videogame I can't pause and have a controller or kb/m in my hands. I don't have to leave my phone in view to make sure I notice my girlfriend texting me because it pops up on my wrist (which again, I can respond to with voice without my hands ever leaving the controls).
So on and so forth. Maybe none of this applies to you. But that's not the point. The needs of a tablet don't really apply to me, but for someone else it's more convenient than a desktop for their needs. Everyone has different needs and a smartwatch fills a lot of mine.
As for price: I'm not sure why you think they'll never drop. We already have decently functional AndroidWear watches for $200. I could see that same watch being $100 less in a few years easy.