Some smart words from Peter Sikking on the subject of why we need more fonts: http://blog.mmiworks.net/2017/06/the-world-needs-more-fonts-honestly.html?m=1
I'm no stranger to this topic, of course. On the one hand, it's kind of funny that it seems to plague some disciplines more than others; on the other, I suspect that it's just a sign that people are underinformed about what your entire field is. I know my brother regularly faces the question "but why do we need to do $Physics? What good does it do?"
(Which, basically, means they expect you to have some three-point connect-the-dots 'it cures cancer' reply, in his case. My go-to answer for typefaces is different)