Yeah, you've hit on what really appeals to me about those three and others like them. They shift focus to what's really important in each case.
In HTML I want to focus on document structure, not closing my tags. In CSS I want to focus on style and visual consistency, not nesting. In Javascript I want to focus on application behavior, not semicolons.
Last time I looked into sass/scss/less, I decided Stylus is for me. Looked into that? Not just getting rid of semicolons and curlies, but even colons :) plus macros, functions, variables, calculations, all the "usual" stuff.
One of the reasons we did not switch from HAML/SASS/SCSS to LESS/Jade/Stylus is the output. HAML and its cousins do the extra little things to help developers diagnose problems like adding comments with the original line # and file; pretty-printing, etc. All these options can be disabled for production of course.
In HTML I want to focus on document structure, not closing my tags. In CSS I want to focus on style and visual consistency, not nesting. In Javascript I want to focus on application behavior, not semicolons.