It's a hassle to keep multiple devices charged. If 80% of people have the mental bandwidth to keep their phone charged daily, I'd say less than 50% would be able to do the same for 2 devices.

Part of the reason people like tablets as a second device is that you can turn off the screen and it'll maintain a charge for several days. If it had to be charged as frequently as a phone, people would just stick to their phone.

You don't have to unfasten a phone to charge it.

Heh, just to weird you out, I'll share that I charge my Pixel 5a phone about once a week and my Garmin FR255 watch about once every two weeks. And that's while recording about 5-6 hours of GPS tracks per week on the watch.

I spend a lot of time in front of large screens, so my phone is mostly there in standby either to let someone call me or to do a quick check when away from a better computer.

If I'm going somewhere expecting a call while my phone is pocketed, I might look for call notifications on my wrist. But otherwise I'd rather just poll my phone infrequently. Since I'm not enslaved to notifications, I usually turn on the bluetooth link once weekly to allow the watch to sync health data and refresh its cache of GPS ephemera for quick location fixes.

When I commute regularly, the ~25m plugged into my car to and from work will keep my phone going all week. When I work from home, I'll be charging it every other day, or piecemeal on a wireless charger when I remember.

I love my mechanical watches because a few twists on the crown gets it moving and the automatic movement keeps it wound the rest of the day.

I do but the phone is much more useful and doesn't require a special charger. I might start using it again at some point.