That is exactly the case. And managers are the main reason that people leave companies as well. This video talks about this challenge: http://www.youtube.com/watch?v=CM0RO3qnLMg
Agree, it's a combination of both, as well as some other challenges. Yes, it's a culture that seems to support these behaviors broadly across the organization, a leadership team that isn't demonstrating the right behaviors and managers that are emulating their leader's behavior. There are definitely opportunities to change processes, behaviors, beliefs/thinking to tweak the culture, as well as give their managers training on how to get the best from their teams and support the company strategy.