High staff turnover is a bad thing. Pretty much everyone would agree on that - especially for a development team where knowledge of the system is essential.
In fact surely keeping staff happy - retaining the best talent - is a priority for all managers.
But when the pressure's on, IT managers will end up cascading the misery to their team for the simple reason that all managers are primarily judged on and therefore incentivised by meeting project deadlines.
Meeting deadlines means meeting budgets and delivering ROI. In other words, it means making money - and this is the only priority of any company anywhere regardless of what their website says about CSR, diversity or people development. Money is all they care about - make no mistake.
So what does this mean for you as a developer? It means that the only person you can rely on to look out for you is yourself. If you regularly bend over backwards to meet deadlines then that becomes the norm. If you join the Working Late Gang, you give them strength in numbers - it becomes the culture. The unrealistic expectations, the flawed process, the poor planning - all of it is hidden or condoned by you picking up the strain and making it happen.