[astura]

It's not a "necessity," it's a personal preference.

I started out programming on a dark theme (the emacs default) but I've used a light theme professionally for about 15 years (and no other dark applications). I prefer the light theme and I don't find it hard on my eyes one bit and I have astigmatism.

[aepiepaey]

The Emacs default is bright (black text on white background), not dark.

The exception is if you're using it in a terminal, in which case it re-uses the terminal's colors.

[astura]

Well, the emacs theme installed on our school computers was a dark theme. This was way back in the day.