You often do math on the whiteboard or on paper, and it involves repeated references to the same things, which might take forever to write out at each step. Add

You often do math on the whiteboard or on paper, and it involves repeated references to the same things, which might take forever to write out at each step. Additionally, since it's a 2d notation, the "shape" of the formulas is informative, which is an aspect you lose with bigger names.