The issue you're overlooking is that these management consultants are being paid large fees for information that a company can get for free just by listening to their existing employees. However, that's not a slight on the management consultants themselves (nice work if you can get it), but is a slight on companies that don't trust that their employees can give them sound advice. Problems at the ground level are going to become apparent earliest to those working at that level, if you ignore that feedback you're potentially throwing away valuable information.