I'm not sure it necessarily attracts users, but we've got a lot of positive feedback for adding support to our website and app for dark more on Noora. I also personally prefer darker themes, so it wasn't a tough choice to implement one.
I don't think it's something to attract audiences, it's a bit of an overstatement...but it definitely helps sometimes (ex: on YouTube, I keep switching between dark mode and light mode, depending on the time of day or my mood)
Kive