Usually it doesn't matter what it's written in, because unless a company wants their site to look like a template, everything will be overwritten. And the valu

Usually it doesn't matter what it's written in, because unless a company wants their site to look like a template, everything will be overwritten. And the value of the base idioms will still be retained for the dev team. Since this looks like it's to help create a consistent look & feel for Office UI, I'm not sure why they chose LESS. :) Most likely that's what they were familiar with, and maybe they wanted to keep dependencies low. But there's always Stylus [1], and it's at least as powerful as SASS. Plus it has better macro integration, which is very convenient when you forget to call @mixin. Sytlus "border-radius: 5px;" vs SASS "@include border-radius(5px);" The main reason LESS isn't desirable is it's very restricting & has no lexical scoping, which makes writing plugins such as spriting very awkward to write. [1] https://learnboost.github.io/stylus/ https://learnboost.github.io/stylus/