Earlier quoted context omitted.
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.
None of this applied to the people I've worked with who preferred it in IntelliJ. I'm willing to mark it up to personal preferences that I'll just never understand, alongside why great directors keep casting Leonardo DiCaprio.
And that list wasn't intended to be comprehensive.