The purpose of typography is to communicate. That is its essential function. Any classical definition will tell you that font families and typefaces exist only to craft the most effective message for the most appropriate audience. Any design, therefore, that works to undermine that goal is a suboptimal type.
That is why teachers should care about typography. They are both in the communication business. In fact, if you take the classical definition above and replace a few words, it sounds like a fairly appropriate description of the role of an educator: to deliver information and to design insight.