Because precompilers are sort of a disruption of the point of CSS to begin with. I know, I know, a lot of people use them, but using style sheets that require compilation pretty much defeats the purpose of separation.
Yes and no. The browser has to parse the CSS, and it's most likely building an abstract symbol tree. So in a sense CSS is compiled too, it just happens in the browser so web developers don't have to be aware of it.
Do you remember the type attribute?
<style type="text/css">...</style>
That was originally put there so we could have different types of stylesheet languages, instead of everyone having to use CSS all of the time. Maybe browsers should incorporate the most popular LESS and SASS projects so that they can support type="text/less" and type="text/sass" too. Some workaround will be needed for old browsers (a javascript shim that retrieves server-compiled css) during the transition period, but eventually we'd end up with being able to use LESS, SASS, and CSS where needed, interchangably.
Do you remember the type attribute?
That was originally put there so we could have different types of stylesheet languages, instead of everyone having to use CSS all of the time. Maybe browsers should incorporate the most popular LESS and SASS projects so that they can support type="text/less" and type="text/sass" too. Some workaround will be needed for old browsers (a javascript shim that retrieves server-compiled css) during the transition period, but eventually we'd end up with being able to use LESS, SASS, and CSS where needed, interchangably.