I’d add to the other replies by saying that this isn’t just pure inefficiency - it’s the ability to try things and get them wrong without dying. Often several things. If one of them works out, maybe they justify the rest - just like investing in startups, ironically.

Second, it’s also about redundancy, having more employees covers you from key man syndrome where your operations could be adversely affected by an employee leaving. Even if it means you technically have more employees than you need at a bare minimum.

Third, I’d argue that the level of “efficiency” required by a startup simply isn’t sustainable in the long run, unless you want everyone to burn out. Successful companies likely span a spectrum of efficiency, but none of them need to be on the far efficient end like startups do, and that’s better for everyone working there.