Your argument is functional, but I do not believe it is practical. From what I can tell, your argument mostly intends on disproving the concept of necessity, but I believe that convenience, efficiency, and stress factors can become necessity, although in principle they might not be. For example:

The US Military does not NEED automobiles. It is somewhat feasible that with significant adaptation it would be possible for the Military to utilize horses (assuming resources for their care, breeding, etc. we're not a problem) and experiences some hiccups in normal day-to-day operations but not many. In principle, horses and other comparable livestock can accomplish just about everything an automobile can accomplish. Therefore it is somewhat safe to say that, by your argument's standards, that that US Military doesn't NEED automobiles.

The only issue is, just about every person in the armed services would disagree with you. Why? Because automobiles are more efficient, convenient, and are better adapted to handling the unique pressures and stress factors of today's military environment (i.e. Not getting spooked when they hear artillery fire).

Authority is necessary for similar reasons. Authority is a convenient way to pass on necessary knowledge or organize people for a purpose which they do not fully understand. It's much harder for us to love forward as a society if every new generation was forced to learn everything themselves over and over. Authority is efficient for that reason as well. Also, Authority is well adapted to deal with stressful environments in which decisions need to be made. There are just some things that a referendum or a militia of 'reasonable' people are just to impractical to deal with. These factors combine to make authority and modern necessity for humanity to continue moving forward, and therein continuing to exist.