No they didn't use them because they ran out. You know nothing about mathematics clearly. There are conventions to keep it concise. Some definitions of simple things would be unreadable if you used longer names. Consider the quotient rule:

    k'(x)=(g(x)f'(x)-f(x)g'(x))/(g(x)^2

Or in your world apparently

    quotient'(expression)=(left_expression(expression)right_expression'(expression)-right_expression(expression)left_expression'(expression))/(left_expression(expression)^2

Yeah, no.

Surprisingly I've just gone through the last 30 pages of mathematical work I've done and there's a couple of π in ∫ there and that's it.