I'm going to second this. I've seen on more then one occasion that some people believe it's their job to do this on order to be most effective. I literally had PM tell me (as head of engineering) that they thought it was there job to set unrealistic expectations and adversarial environment in the hopes that it created an environment where the engineers worked longer.

I'm reality it creates a hostile work environment where burnout is high, morale is low, and projects take even longer to finish. It sacrifices all long term gains for short term results.