My subjective and personal observation is that LCD panels represented black by turning on the pixels to become opaque and stop the backlight from pass through the panel. This strategy worked well to get to relatively black pixels but a few years back typical consumer LCD panels were not very good at this and allowed a significant amount of light to pass through. When applied to large areas of the screen this, at least to me, made the screen look wrong and not enjoyable, specially after being exposed long enough. Therefore, as the user experience with non-dark modes was better, dark modes were simply not used.
Nowadays consumer-grade LCD panels are able to represent better contrast, thus the overall experience has improved.
My 0.02€.