> 1. You don't have to use it if it doesn't seem useful to you.

Other people will use it and chances are you will have to deal with it sooner or later at $dayjob or whatnot.

The group in 3 can use SASS. At this point you should view CSS like assembly, convenience functions go at a higher level.

> At this point you should view CSS like assembly, convenience functions go at a higher level.

CSS isn't assembly; it's higher level than that. I get why some want to treat it like a low-level language but it's not that, which is pretty obvious if developers take the time to understand CSS at a deeper level than just something a preprocessor spits out.

Also, CSS has to work in environments where using a preprocessor isn't an option—it's not just for glossy VC-backed websites. A preprocessor and all of the other tooling front-end developers use aren't an option for the vast majority of content management systems and wikis for example.

CSS still has to work in these environments.

I hope web standards decisions are never made starting from the assumption that there's a build tool.