There are several possible answers to the question. The first is that in fact, almost from the very beginning, dive watch manufacturers have touted their wares as having benefits relevant to both diver and non-diver alike. This was probably more true in the 1950s than it is today – case manufacturing precision, as well as improvements in seals and gaskets, mean that the days of it being advisable to take off your watch before washing your hands are long gone, and virtually any mechanical watch from a Seiko 5 on up is going to be able to tolerate splashes and even brief periods of immersion, and emerge none the worse for wear. (I wore my first mechanical watch, a Seiko 5, into the ocean every summer for several years. I happened at the end of that period to have begun doing watchmaking as a hobby and out of curiosity I took the back off the watch, curious to see what it was becoming clear to me, was injudicious behavior, might have done to the innards. There was a hint of corrosion around the inner part of the crown tube but that was it). However, though it may be less true today than it once was, the habit of thinking of dive watches as generally a significantly more practical and pragmatic choice for daily wear than non-dive watches, is probably permanently ingrained at this point.