A very large portion of lamps purchased at home goods stores have dimmer switches (a knob that you turn instead of flipping a switch), and dimmers have been widely available at home improvement stores for decades. This idea is not some niche thing limited only to smart home tech people. It doesn’t have to be automated—one can just get up and set the brightness to their liking.

I think the big surprise for most people would be that many LED bulbs are not dimmable, as that hasn’t been something they had to worry about with older bulbs (it was also an issue with CFLs, but people avoided them because of the harsh color)

I agree that it's probably still niche, but judging by the expanding section of smart lighting at my local Home Depot, my guess is it has gone beyond techies at this point. Home Depot definitely doesn't cater to tech folks.