This may be true, but in my experience(not very wealthy, typically sub $400 devices) the presets are set such that 0% backlight in the OS is glaringly bright. I cannot turn it down without rooting the device.
Color temperature can also be a problem, but there's a lot of awareness of that issue nowadays. Most operating systems now support automatic adjustment of color temperature based on time of day, plus manual adjustment. Devices that adjust their color temperature to account for ambient lighting are starting to catch on, and I expect they'll be pretty common in a few years.