I find dark mode absolutely necessary on my modern flat screens. Why? They’re calibrated to DCI P3 (HDR), and a 32" white field is actually painful.

All the phones and tablets I’ve had have been OLED, and I’ve been using dark mode on them for years — just because it’s easier on my eyes.

You’re right that dark mode is not new. I started out on IBM P38 ‘green screen’ terminals aaages ago. (and mechanical switch keyboards, which have also come back).

‘Cool’ has nothing to do with it — it’s all about being comfortable.