Well that is a user setting, and I tend to think the first retina iPhone is what started the trend.
Also, at certain screen sizes, 1:1 scaling is just impractical due to limitations of the human eye.
My 27" 4K screen is pretty much at my personal limit in terms of what I can handle at 1:1 scaling for my normal viewing distance. Had I gotten a 24" 4K screen, I'd have to set the text scaling to ~125% which would also translate into some lost screen real estate.