No I don't think national parks should be sacred, but I don't think they or public libraries should "be butchered for 'floor space'". I think options should always be measured and considered.
Libraries taking up too much floor space doesn't mean much, since so does anything else. At the same time, they and all other things also take up too little floor space, since "taking up floor space" by itself doesn't really mean anything I can discern. Libraries are unique, and valuable; what other unique and valuable thing does their existence prevent?
To measure things you need at least two things. Maybe even three: an object to measure, a scale or another object to compare to, and some sort of heuristic as to what the result might mean (for you). It's pointless to say that it doesn't satisfy your standards of "usefulness" or what exactly your concern is, if you don't share those standards.