In general I think it's fair to say that math has lots of crazy and just plain poor choices of conventions and notations that no sane person would ever think of now; it's just very hard to change something so widespread and ingrained, especially given the extremely cryptic and dense notation that leaves no room for evolution without ambiguity (and it's already hugely ambiguous since of course you can't prevent new concepts from being necessary, so syntax gets reused pretty confusingly, and haphazardly at that).

To put it this way: maths is the legacy codebase from hell; but it's what we have.