It isn't easy:

  - to have no build toolchain
  - to work without javascript
  - to have single configuration points

To be fair, things like SASS and LESS have been out there for a while. Tailwind requires build in production.

I think we're talking 1995-2000 here, not 2006 (when sass appeared), 2009 (when less appeared), or 2018 (when Tailwind appeared)