Why I use light mode
There's feeling in the developer community that says if you're not using dark mode, you're not a proper developer. Every screen shot and every video you see of someone coding, whatever application they're using, it has a dark theme.
I know this is because it is easier on your eyes. Which makes sense: on screen reading black on white or white on black is hard. You need a little less contrast than that (but not too little so it's impossible to read!)
However, I have a chronic illness that can be made worse by bright screens, so I turn the brightness down. My laptop and phone are both set to around 20%. It means I cannot see my phone screen at all when I'm outside. And I also can't read text in dark mode, except in natural light when the sun's not out.
So I have to use light mode. I don't have that problem with looking at a white background because it doesn't appear white - it's grey in 20% brightness.
Light and dark themes are equally good; you can be a good coder no matter which you use; whatever works for you is the right thing to do.