Well, there have been a few instances in the past where I've been desperate to hire and I've brought people in against my better judgement. I can tell you it sucks having to look someone in the eye and let them go because they couldn't keep up with the rest of the team. Once you've had to do it a few times as a manager, you become more conservative with your hiring.
Sure, pushing pixels around is easy, but when you're up against a deadline and the app is crashing in a subtle way, you need engineers who have solid debugging chops. Not everybody does.
No, that's not what I'm saying. I'm saying it's the manager's job to secure enough time for a product to get developed by the team or reduce the scope of what's going to be developed by working with whomever is setting these deadlines. If you need to magically speed up your development to meet the deadline or work extra hours, the manager has failed at doing the above, something that's a core part of his job. In some really bad companies, the manager won't have a choice in doing either, and you're in a situation where the deadline was simply unreasonable. In those cases, I can excuse the manager. Mostly though, deadlines are artificial and it really doesn't matter if they're met or not. Even if it does matter, the manager is getting paid a whole lot of money to manage both the team and the expectations of those who care about the deadlines. Making the team work overtime is thus a complete failure on his part both to the team and to those above him.
I don't disagree with you that death march schedules are bad, but I don't think I was making a case for them. :)
Another way to put it is that the manager's job is also to hire the best team possible, and there is a wide variance in skill levels of engineers. All other things being equal, hiring engineers who are more adept is a big advantage to the company.
Sure, pushing pixels around is easy, but when you're up against a deadline and the app is crashing in a subtle way, you need engineers who have solid debugging chops. Not everybody does.