Usually mathematics is hard to understand if a subject matter is new. Most of the time there are some common examples that everyone learns about in a subject, and you learn to notate them along the way. When you write new mathametics you try to stick to the conventions from those examples.

The common way you learn mathematics, the notation comes automatically, and new mathematics is often understood as a variation on the examples you learn.

Some of these conventions you probably know, like having i for the varying number in a sum or product (or loop in programming) which goes up to an integer n.

If you called an integer f or a complex number n it would make it much harder to read.