What if your users prefer the look? I presume you don't just publish your site for your own consumption
Then they're SOL. Maybe a competitor will come along with the exact same features/pricing and a robust theming engine, then we can talk.
For a service or brand, it's probably a good idea to deliver a dark mode at some point (especially one that people are forced to stare at for extended periods).
The dark theme is 10 lines of CSS.
Your site is very minimalistic, and that is fine, because it's your site and it's what you like and it's your hobby. I'm less of a minimalistic person, so dark mode would require thought on how I would present a dark theme to users other than just coloring black and grey or white. That's too much work for me and it's personally not interesting (mostly because I do not like dark themes).
I can see why many would not bother. It means keeping at least 2 sets of colors going. Try putting green text on a grey background for example and you are going to have a bad time. It means making a lot of choices you already made and feel you are not going to get much out of it. I have seen many applications botch it. Thinking all you have to do is toggle the background to something dark and call it a day. It means probably means a redo of all of your art assets, and at a minimum what font colors you are using and making everything respect it.