I get a lot of dirt on mine because I wear it all the time... including doing yard work for several hours in 90+ degree heat. I usually rinse it off in the sink whenever I take it off to take a shower... keeps it pretty clean.
Or maybe he hadn't considered getting a watch wet, either. I had a coworker who would say, "I'd never get an expensive watch wet," to which I responded, ".... I'd never spend good money on a watch if it couldn't stand up to some water."