Crazy as it seems I actually just want to tell time. I have to keep a close track of time at my job, so checking my phone for it is a hassle. Plus, frequently looking at one's phone can come across as rude if people don't deduce that you're just checking the time.
Stopwatch function is also for work. Date function is because I'm a flake who can't remember what day it is.
ETA: okay, also, if you've seen the film Touching the Void? It's terrific. The guy is in this life or death situation and he forces himself to crawl on a broken leg toward survival by being like, 'Okay, in twenty minutes, I'm going to get to that rock.' And then he sets a goal for the next twenty minutes. And I was like, that's a great technique. So I feel like I should have a watch just in case I'm ever fighting for my very life in some extreme situation. Or if I travel back in time and have to pilot a ship across the Atlantic or something.
I mean, really, even for everyday circumstances, it's useful because I have a very poor sense of time passing. If I had enough sense of time to know that I should check the time on phone, that would be half the problem solved.