I have lots of eye floaters which annoy me when I'm looking at bright uniform surfaces, such as white paper or white background, but I hardly notice them with dark mode.
This is why I use dark mode too – and it's made a huge difference for me. My floaters are particularly noticeable on white-backgrounded screens/webpages on my 43" external monitor where because, I assume, my eyes have to dart across greater distances than when I'm using my MBP 14".
Yup I've had also had some show up in the past while (got it checked out to make sure no concerns), and looking at a very bright screen makes them _very_ apparent. I already preferred a darker screen but this just sealed the deal.
Came here to write this exact comment. Floaters are distracting and break the flow. Dark theme means less distractions. This was probably the easiest choice I made in my life.