Basically, why SCSS, instead of SASS? The shorthand of SASS was the main reason why I picked up SASS, I recently came back to it and realised that it is no longer in favour. Any reasons why?
Sass has two syntaxes. The new main syntax (as of Sass 3) is known as “SCSS” (for “Sassy CSS”), and is a superset of CSS3’s syntax. This means that every valid CSS3 stylesheet is valid SCSS as well. SCSS files use the extension .scss.
The second, older syntax is known as the indented syntax (or just “Sass”). Inspired by Haml’s terseness, it’s intended for people who prefer conciseness over similarity to CSS. Instead of brackets and semicolons, it uses the indentation of lines to specify blocks. Although no longer the primary syntax, the indented syntax will continue to be supported. Files in the indented syntax use the extention .sass.
Source: http://sass-lang.com/
If you like sass more than scss you are free to use it! scss is for people who don't like the indented syntax. And it is extremely easy to convert a css file to scss beacause scss is a superset of css.
That it is no longer in favor is probably because the developers like scss more. But this is a matter of taste. I personally still prefer sass.