Why do people use color schemes when programming, is it cause it looks cool, do they think it makes them more productive, is it cause some people insist on it makes it easier to read code? None of these statements have been proved as far I know, so why?
Some people (or even a lot of people, I don't know) think it helps them read code if different syntactic elements have different visual appearances.
You seem to argue that they "shouldn't" feel that, since it hasn't been "proved".
Sure, you can do a study and somehow try to measure if some dimension of understanding is more easily acquired with or without syntax highlighting, but what would be the point? To then force those who like it, to not use it anymore? Why?
In other words, if you like Cubist art, or hamburgers, or tofu, do you require all of those to be somehow "proven" before you're allowed to like them?
If you are spending a significant portion of your work day staring at a code editor, surely optimising it somewhat is worth it.
I only code a little in my free time, but have a dark background makes it easier to stare at the screen, and having, say, variables a particular colour makes them stand out when scanning through code.
It's like a professional cook having all his kitchen utensils laid out in a particular manner that's efficient for his work routine. I'm sure there's plenty other analogies from different professions you could apply.
Very few things have been "proven" in the sense you are talking about. People still have to make judgments about them anyway. By and large, most developers seem to have concluded that syntax highlighting helps them in some way.
Possible reasons why:
1. Distinguishing different types of operators/primitives/objects from each other at a glance.
2. Aesthetic enjoyment.
3. An appropriate color scheme may be "easier on the eyes".
I began using a darker background in my text editor last year due to a sudden increase of eye floaters that was distracting when I stared at bright backgrounds. While now I can ignore them on my own most of the time, I still prefer to use darker themes when applicable.
