Companies grasp one thing quite easily and it's their bottom line. Maybe, agile is not delivering better enough to have an impact on the bottom line and all this discussion is, well, moot.
That being said, in my training I give several examples of Agile companies that either have no management or very flat hierarchies, such as 37signals, github, Booking.com and Valve. There are many reasons why they're successful and it would be silly to simply say it's because they're jettisoning management. However, we know that large companies tend to be significantly worse at innovation (Steve Jobs is an anomaly) and they also often focus on risk avoidance rather than reward.
The primary strengths of many large companies is name recognition, financial reserves, and mature products. That's very hard for smaller companies to compete against, particularly given the old saw of "nobody got fired for buying IBM/Microsoft/$insert_large_corporation_here".