It's not efficiency itself that's the sole metric, it's the ability to find a job in the first place, easily, fluidly, in a dynamic economy that lets business owners and workers both experiment fairly smoothly. You cannot have this without foregoing heavy handed worker protection laws. It's such an obvious bloody thing but apparently some people get so emotionally blind-sided by the notion of "companies firing = bad" and immediately assume that such a right always boils down to "greedy businesses". It does not.
Put yourself into the other shoes: You want to start a business, you have limited resources, you want to hire people who can help you in exchange for compensation and these people want that compensation, but the laws where you live make it nearly impossible to fire anyone you hire. What will you do? Be realistic, looking at your actual finances and human self.interest as objectively as you can.
Businesses are the private organizational expression of private people (or groups) using their personal resources to try to earn something more, improve their economic well-being. Saddling them with the ideological notion of being make-work resources just because they started something of their own that required employees for fixed aims is absurd.
It also promotes informality and labor black markets, in which people who prefer actually getting a job and money for living expenses to "enjoying worker protection" in the abstract but having it basically impossible to get hired legally in practice. So they accept being hired under the table. Now that they're working informally, as if they were illegal immigrants, they're even more open to abuse than they would have been if they could just get hired and fired easily, but at least formally, and under at least basic rules of minimum wage and labor law.
A simple analogy would be you hiring a gardener to trim your hedges and mow your lawn and then being forced to offer him work any time he asks for it from then on. I doubt you'd accept this. In fact, I doubt you'd even hire gardeners ever again.