Traditionally, one example is software that supports theming. Site owners who wanted to customize the look of something without getting their hands too dirty wr

Traditionally, one example is software that supports theming. Site owners who wanted to customize the look of something without getting their hands too dirty writing a whole new theme may duplicate and heavily modify the CSS from an existing one. For applications people spend a expected to spend a lot of time in, the user may even be able to select the theme. But, things like CSS custom properties have eaten into some of the basic use cases like palette swaps, assuming they're supported in the default theme.