Week+ battery life, truly always on, sunlight readable, much smaller size/thickness and thus more comfortable than all other smart watches.
For me, the use case of a smartwatch is notifications. It lets me keep my phone on silent all the time without missing important messages or calls. Proper filtering is important so you don't get notification spam on your wrist but some notifications truly are important and checking them without taking out my phone, and even sending a quick reply, is awesome. I also use the "extend unlock" feature of Android which works with any Bluetooth device but especially well with one that is always on your wrist. Locating a lost phone is another great feature. Timers and alarms are a given of course. Maps navigation directions on your wrist can also be useful (but you get this for free with a proper implementation of notifications).
To me the paradox of the wearables market is that it seems like the only reason people buy them is as fitness trackers which they are actually pretty bad at. The numbers they report might as well be made up in many cases, and the weird metrics they provide aren't useful. The sensors make the watch thicker and less comfortable too. Meanwhile, it's actually super useful to have phone notifications on your wrist, but people don't seem interested, and e.g. Android Wear really sucks at it. (Can't speak for the Apple Watch as I don't have an iPhone, but I've always felt that the hardware design was ugly.)
Look into Amazfit watches. They're about as close as you can get to a Pebble these days. It also has a bunch of fitness stuff (GPS, steps, heart rate), but you can mostly just ignore that. Mine is just for notifications, stopwatch, and telling the time, and a charge still lasts more than 2 weeks on the original 6 year old battery (I've worn it roughly 23/7 since April 2018).
The newer Amazfit Bips sadly don't have transflective displays and do not last a month like the original Bip line used to. Why they killed off the unique feature of this product line and made it another generic LCD smartwatch when Amazfit already has several product lines of those I have no clue.
