Unused RAM is wasted. But used RAM is also wasted, sometimes. If I can accomplish the same thing with less RAM, that's better, because it lets me do other things at the same time. It doesn't mean I'm not going to use that RAM, that would be pointless. My desktop running dwm typically idles at ~50GiB RAM usage from random crap I've got running. But I can prove that the desktop is using no more than like 300MiB.