I can't promise this is how all managers think. And there's definitely companies that are perfectly happy for you to work 60 hours when being paid for 40. Either they don't care, or are ignorant of the qualitative cost of that.

I'm very fortunate to work somewhere that gives me a reasonable amount of autonomy for how to ensure my team delivers quality work on-time. One of the main reasons is that the company doesn't MBA us to death by doing things like, "they're on-time! Give them 20% more work next time!"