For "open-floor plan" I think the explanation is simple: it's cheap(er), and people in charge of facilities/ hr don't understand or care about the tradeoffs. It's funny, in our corporation they call it "space optimization" - I told our sr. director that it's appropriate since compilers also have "space optimization" as an alternative for "execution speed optimization", but he didn't seem to get the irony in that (or more likely, didn't want to, since it's out of his hands/ the layout policies are decided even higher-up, at the C-level).