It's a trade-off between brevity and verbosity, some mathematics do that. Often longer variable names are in ALL-CAPS. Since ab = a*b, it's important to differentiate vars from multiplications.

Yes, it is. I just brought it up because it's an important factor when talking about the need for additional symbols.

Btw, even mathematicians don't mind writing out `sin` or `cos` or `ln` in their formulas. So they are certainly not completely averse to multiple letters.