Because it’s boring.
My favorite from Michael Bierut’s Thirteen Ways of Looking at a Typeface
10. Because it’s boring.
Tibor Kalman was fascinated with boring typefaces. “No, this one is too clever, this one is too interesting,” he kept saying when showed him the fonts I was proposing for his monograph. Anything but a boring typeface, he felt, got in the way of the ideas. We settled on Trade Gothic.