When you look at the articles about Agile/Scrum/Lean, they are all about self-organizing, decentralized, democracy, etc.Those are welcomed by the developers but conflict with managers benefit, because our conventional management is about hierarchy, command and control, chasing the power, the manager cares more about how his boss think instead of how his subordinates think. For managers, embracing agile means loosing power, weaken their benefit, that is why manager don't like agile.
On the other hand, agile is about changing, changing means risky, but the managers care more about the stability of their position, their power, they don't have much enthusiasm to make changes.
So we have a conclusion that developer and manager like two different classes, developers like agile because it brings them benefits; managers dislike agile because it will lose managers' benefit. The progress of agile movement is quite similar with the progress of human's democracy movement.
This sounds discouraging, but this is the fact, that will explain why agile has not become mainstream after 10 years of its movement.Then what can we do? Try to educate as many developers as possible, gradually if agile principles are accepted by most people, then it is quite possible to force the managers make changes. This will take time, but please remember that the manager won't truely embrace agile,just like no ruler will truely embrace democracy.