I've been told that not knowing better is a typical reason (and another reply says so), but my anecdotal contribution is different.
When I'm implementing algorithm, I'll typically be implementing something that uses single letter variable names. It's easier to do with consistent variable names. That's it. I once tried meaningful variable names in LaTeX to make code nicer, but long variable names rendered as math are an unreadable mess, so I went back to short variable names.
That being said, it's not hard to change variable names with a good IDE, and in LaTeX you can alias variable names with \newcommand.
When I'm implementing algorithm, I'll typically be implementing something that uses single letter variable names. It's easier to do with consistent variable names. That's it. I once tried meaningful variable names in LaTeX to make code nicer, but long variable names rendered as math are an unreadable mess, so I went back to short variable names.
That being said, it's not hard to change variable names with a good IDE, and in LaTeX you can alias variable names with \newcommand.