Come again?!?
Here is a text without a font.
You read it, and see the meaning of words.
Letters are essentially invisible.
Here is a text with a font.
You read it, and notice the letters, their shape.
This supposedly creates some sort of an aesthetic difference, valued by "designers".
However, by this point you already stopped noticing the shapes, the letters are invisible again.TL;DR: Using a font gives you an ability to make the users see the letters and derail their train of reading.
P.S. Me cannot to write fiction.