Dark themes are not as readable for me.

Albeit dark themes are more beautiful, in a light environment during daylight, a light background with dark fonts is easier on your eyes.

Because I can't get it consistently. Better to have my eyes adjusted to constant light than be randomly blinded when whatever random site or app isn't dark.

Some types of application I prefer light, some dark. But the premise is wrong:

Saves your battery

Only if you're using OLED, which most people aren't, and by very little. You could save more battery by using a low-power mode when you don't need all the bells and whistles.

Easy on eyes

Debatable, different for different people.

Dark theme is just nicer

That's not objective, it's personal taste :)

I use both. I always have automatic dark/light mode enabled where possible controlled by sunset/sunrise. If it's light outside I just prefer light mode and when it's dark outside I prefer dark mode. Being in a well lit room it's easier on the eyes to use light theme.

The only time I use dark mode only is for Discord and IDEs.

I find it easier on the eyes plus I don't use Oled Screens so I'm thinking "why should I block all this light that my backlight produces anyway just so i have something that looks a little more aesthetic?"

I just find reading on light mode much easier and comfortable, so i use it most of the time. I do use dark mode for programming, it doesn’t bother me there, but for most apps and websites the dark mode feels much more tiring.

Dark mode just looks bad aesthetically, IMO. Maybe it's something to do with my ADD, but I can't focus for long on apps or pages using dark mode. They're boring to look at.

I just toggle based on time of day / lightness of environment.
I find my eyes are more strained when using light text on dark backgrounds in a light environment (and of course dark text on light backgrounds are a no-go at night). The only exception to this is my phone, where the battery gains from oled makes dark mode the only option for me. I hope Kbin gets a nice light mode toggle that can follow the system theme in the future.

I'm just used to it, I guess. I've never had an eye strain issue with monitors for some reason. I'm resistant to change. Moving to Lemmy from Reddit was a big deal for me, and not just because I had sunk 13 years into Reddit, just the idea of changing something I'm very used to... there was a reason I still used old Reddit.

EDIT: That said, I spent countless hours on my old Apple IIs with their famous green-on-black monitors.

I have photophobia (and photosensitivity!) so dark mode is the only tolerable way to look at things for me.

Since dark mode has become a lot more prevalent/accessibile there's been a notable reduction in headaches/migraines for me, especially in conjunction with 'night light' settings, and an anti-glare glasses coating.

Dark theme gives me a massive headache after just 5-10 minutes and I think it's because the text is fuzzier to me. I'm not sure if it is astigmatism related?

Weird thing is that AMOLED dark on my phone doesn't bother me the same way.

Also colors in dark mode when I'm coding seem to blend together more so I am not as quick at picking up visual cues.

I never understood why go dark only? We have a neat feature in almost all the device change depending on the brightness or sunrise, that is the way to go IMHO.

White UI looks nice as well.

while I would say I belong to the dark-theme cult, there are some applications/websites that I cannot get used to them in dark mode. Like github or slack for example in which everything else than they light theme looks strange in my eyes.

Since Thinklight is no longer a thing, how else am I supposed to read my credit card info off the card?

both and as long as not grey text on dark theme

I primarily use dark themes but I do switch to light themes from time to time. To see better, give my eyes a break, or when in a dark room for too long are some examples. Also some apps just don't play nice in dark themes.

why?

They are Heretics and Miscreants, an Abomination unto GoD who spread their lies about "The Light".

Memmy has an option I love. You can chose a any theme for system daytime and a different theme for nighttime. So I chose Dracula for day time and OLED dark at night. The full black OLED theme is too flat for daytime but the dark Dracula is perfect.