Don't forget handwriting here. For all these centuries, and perhaps even today, the vast majority of both writing and reading of mathematics wasn't typeset: on

Don't forget handwriting here. For all these centuries, and perhaps even today, the vast majority of both writing and reading of mathematics wasn't typeset: on blackboards and in lecture notes, and on paper in the many attempts to understand what someone else did, and in turn to work out results that may one day end up on a printed page. Introducing an easy to read & easy to typeset notation which doesn't work well by hand means you're creating a figure, an illustration to be looked at like a photo, not something to be worked with.