If my son sees a picture that has a limited color pallette, it’ll be on Instagram. Back when the Web was new, however, a lot of video cards and color monitors could show only 256 different colors (8-bit color) on screen at once.
With 8-bit color, photos appeared grainy because the computer had to use dithering technology to approximate more colors than it could actually show at once. Even the desktop wallpaper and icons in Windows looked pixilated when used in 8-bit color mode. When I finally got a 16-bit video card, the entire Internet looked different.