This is a good point. On any sizable site, especially one that has evolved over time, you can't really remove CSS, it just gradually accretes more and more. But most of the rules aren't even used on most pages. Being able to first remove anything not used, then remove anything that gets overridden in the cascade, could reduce CSS down to a tiny fraction of its full size (never mind comments and spacing). But would that give better results than loading a big bloated and wasteful CSS file once and caching it for the entire site (or many sites in a case like CDN'd Bootstrap)? Either way is one form of bloat and waste or another.