If you're using dependency managers like bower you either have to import the stylesheet in your <head> or use the @include in a sass stylesheet, both will be a new HTTP request. Whereas if you compile it in one file, you save an extra request (now imagine you use multiple dependencies each with their own css file). Renaming a file would defeat the whole point of dependency management.
For some people it is, I used to use CodeKit too (and I've used the beta) but at the moment I prefer using Grunt/Gulp, it provides me with more control over the building and others can use it easily by doing npm install.
But I assure you that there's definitely a market for tools like this.