Well managers have an important role in business. They MANAGE things haha. But in order to have a healthy organizational culture, they have to be friendly, and approachable. Sure they can get away with the "I'm the boss approach." But what this does is create fear from employees who only do what it takes to get by. If you want your employees to go above and beyond what you ask of them, they will on their own if they think their manager not only cares about, but will listen to everything they have to say, including new ideas and such.
It's the equivalent of your boss saying "Get that paper on my desk in an hour or you're fired." and saying "I need that paper on my desk in the next hour or so, so we can work out this business deal. If there's something you need let me know. Keep up the good work."
They will both trigger too completely different responses.