There is a difference.
Whereas people may have accepted that heavy phone usage may mean it doesn't even make it through a day ... are the masses going to be okay with the same for their watch?
where have they accepted it? people constantly whine about the short battery life of smart phones. They just learned to live with it because the increase of functionality just came with this trade-off. Also, a Smartwatch simply isn't "a watch". It's a companion device that you just happen to wear on your wrist, instead of a watch. It's not "replacing your watch", it's extending your phone to your wrist.
whoever wants a less functional watch with great battery life should either get an analog watch. If they wanted smartwatch features, though at a lower fidelity, they should opt for a pebble.
thank god there's enough options along the spectrum of functionality -> longevity.
and as some have pointed out already: There's plenty people who take off their watches when going to bed already, for not-battery-related reasons.
sure its possible... but that really doesn't make your life easier. People put up with short smartphone batteries because the smartphone can do so much, the extra hassle of nightly charging is worth the utility it provides. The smart watch doesn't really add any killer features, just extended your phone to your wrist. I'm not convinced its worth the extra hassle at this point.
some would consider that a killer feature already
my grandma doesn't care about smart functionality either, so a dumbphone is all she needs. And there's people who use their smartphones exclusively for texting and making phonecalls and they're fine with charging it every night, too.
it's just not as big of a deal as some make it out to be, right now. Sure, there's plenty of room for improvement, but right here, right now, the tradeoff exists, and it's a perfectly reasonable for a lot of people.