I had your line of thought until I got a smartwatch. On my second now (Pebble first, then LG Gear) and yes, leaving your phone in your pocket IS the killer app. Knowing if that email alert is important, glancing at a text and flicking off a quick reply, being able to feel notifications in a noisy environment. Most importantly, my phone now goes all day on a charge due to the decreased amount of screen on time. I know the form factor isn't for everyone, but it can be very useful and shouldn't be outright dismissed.