It would be better if we were able to add FONT families and Typeface to a project or the application framework instead of to the computer. Many instances of ArcGIS within organizations run on virtual machines. While I can add a new font to a VM. The next VM session is not going to be on the same VM.
I found this problem when creating a map with Alegreya font. I was matching the font used in the Modern Antique basemap. The map does not throw any error when opening on a new VM. The new session will switch out the missing font for the default font, which is Arial in my case.
I know that I could reinstall the missing font on the new session. I may request to have the font added to the next VM image. Maybe I am missing something like adding the font as a text style to make the font work no matter which machine it is running.