When it comes to their departments, the power of a DP is absolute. The camera and lighting crews have one boss and the DP is it. However nutjob his ideas seem or whatever harsh demands he has, his crew performs them with what should be minimal complaint.
Outside of his crew, the DP has a hierarchy of folks above him who he has to answer to. The director, the producers, studio execs, the Union—he's far from autonomous.
Whatever power a DP has pretty much vanishes when off of the film set. The average Joe won't be impressed by his stellar Steadicam skills, and won't bow to his every whim as the members of his crew will. This may cause him a little confusion the next time he’s in line at the DMV.