It was true at the time. But as times have changed, the answer to this question too if you think about possibility to do transitions in CSS and define key frame

It was true at the time. But as times have changed, the answer to this question too if you think about possibility to do transitions in CSS and define key frames for those transitions. Things previously done in Javascript are now (partly) possible in CSS only. With that it makes sense frameworks for CSS. It does not matter if the framework is mixed in by SASS or LESS, because from that point of view you could argue that Javascript frameworks are not required, because they could be mixed in as well.