Is there a way to improve the readability of equations in research papers?

I read a lot of computer science papers, and have to understand a lot of equations. Most of the time the concept is so easy, that someone could explain it to me in 5 minutes. I one the other hand need up to an hour to get it.

It is difficult for me to search for the variables in the text, and often I print the paper out and write the meanings of each variable down on the side.

My questions:

So why is it not common to make equations and algorithms more readable?

Is there some PDF reader plugin which highlights the variables in text? Any tips on how to improve in reading such papers?

Why do authors not add an additional list to each equation with a list and explanation of each variable. Should I do that?