There are many strange symbols in math already that can be difficult to type without something like LaTeX. I feel like something pronounceable is usually better unless you have a sufficiently general idea.
> "why haven't scientists come up with more symbols yet?"
Take an advanced math test and try to type it out. Being in no sense historically limited by typewriters/keyboards, you might be surprised at the complexity of the symbols.
I also ask "why haven't more symbols been introduced to our keyboards? Just !@#$%&*..."
It's strange, esp. when you realize coming up with a new symbol that everyone uses is easier these days than it was 4 centuries ago!