I don't get the appeal of dark mode. Do people really like to pretend that they're on a submarine or something?
Some people use it because they have migraines and bright lights trigger their headaches. Some people use it for "stealth" reasons when they want to be online without giving off a lot of light for some reason. Some people are photophobic -- aka light sensitive -- and just favor darker websites generally. There's myriad reasons to want to use dark mode. It's not any one thing.
I try to dark mode everything I can as well as have monitors in reader mode and contrast turned down.