It may be that there are few industries that require it professionally, but just because one's profession doesn't require it doesn't mean that one can't, or doesn't, use it. Consider, for example, Fermat, Young, and legions of other, perhaps less well known, amateur mathematicians (for example, Garfield (http://en.wikipedia.org/wiki/Pythagorean_theorem#cite_ref-Ga...) and Napoleon (https://en.wikipedia.org/wiki/Napoleon%27s_theorem))!