I just had this conversation with someone not that long ago, they noticed I was wearing a watch and I had my cell phone in it's holster on my belt. They wanted to know why I still wore a watch when I had a smart phone.
For me, it's a simple matter of respect depending on the situation. When I'm at work or in a social environment I don't want to be seen as "checking my phone" constantly, seeming to be bored with what I'm doing IE: checking for text messages or emails or something like that. I'm still (though I'm only in my 30's) "old school" when it comes to "toys" at the dinner table I guess. If I have guests over or I'm out with people my time is their time, not conversing on the phone so for just checking the time I'll fall back to a watch.
I also consider a watch to be more or less a fashion item (bracelet for males essentially) more then utilitairian purposes. I stopped using a digital watch (though I still have one) after switching to portable devices back in the early 00's but I've always had my nice watches for social / meetings type gatherings.
When I'm at home or not expecting socialness I'll just check my phone. I also switch wrists to help keep the "farmers tan" down to a minimum.