A few years ago I moved to the Netherlands. Offices and houses here have large windows, and we can enjoy a lot of sunlight during the long summer days. With so much sunlight shining into my working environment, I need to use my computing devices on light mode.
Black text on white background is relatively easy to read in a highly lit environment. Conversely, trying to read white text on dark background is a futile exercise in a sunny room: I can’t see anything with all that glare.
On the other hand, sunset here in the winter is at around 17hs, and most of the winter is dark and gloomy. In a dimly lit environment with just some warm lights, looking at a screen with a white background and black text makes my eyes hurt. It’s terrible for my eyes.
Effectively, I need dark mode when my working environment is a dark one.
While dark mode and light mode are often thought of as an aesthetic preference, I find them to be about usability.