Traditionally, process improvement has come down from management.  It's expected that this is part of management's job, to keep check on the status quo and determine when things aren't working and fix them.   Management assumes that as well, and is always trying to find ways to improve without having impact to others in the organization.  Even if individuals who are "feeling the pain" with the inefficiency are discourgaged to help, and told to "focus on their jobs" and leave it up to management to improve.  Management ends up taking on the entire burden of improving the orgranization on their own.   As a result, because they don't have the bandwidth to improve everything they end up choosing areas of most pain.   The danger is that they aren't looking at the whole picture, and may be treating the symptom and not the cause.   At best, this only helps things temporarily, as the cause is still out there and will eventually hit a new threshold to cause other symptoms.   For those areas that they are able to attend to, it still impacts others in the organization as they have to react to the changes and aren't prepared when they happen.   Also, despite what managers think, they aren't directly "on the battlefield" and don't always understand what is really happening.  Especially, if they don't ask.

I think the model needs to change.  Improvement should be part of every employee's list of responsibilities.   Management's job is to help others understand what goals are most important to the organization and why, and how to measure success of these goals.  If they can do that and people truly comprehend it, then anybody can determine what improvement initiatives need to happen at their particular level.  It's then up to management to make sure that the initiatives are in alignment throughout the organization and depending on the priority and timeframes, make sure that people given ample attention and time to implement them.   Where possible, to reduce the impact to the organization, things should be done parallel to existing processes as part of a "pilot" project and then rolled out when proven successful.  By spreading both the burden and the work across the organization, this will allow more things to happen.  Management is then focused on the "big picture" instead of the "details", which helps reduce the risk that you are treating the problem and not the symptom.  Lastly, by involving people at all levels of the organization, you are assured that the improved solutions are going to work better because the people expected to implement have been involved throughout the process.  Not only do they have more ownership, they are more proactive in their approach.

Improvement isn't (or shouldn't be) just a "management thing", it should be everybody's business!