I'd say it's evidence that the class is self creating, but not specifically that the class is necessary for society to function. It could be for instance that it must necessarily exist, but only as a byproduct of society (e.g. some people have slightly more resources and therefore an advantage to press to get more resources etc.)

Or possibly it's just a consequence of the kinds of society we've had up till now. Perhaps in [your favorite utopia] it's not necessary nor beneficial.

Or that the positions are self-reinforcing, and whoever gets that position first holds it. Which is exactly why the systems that support aristocrats need to be dismantled, and not just the current crop of aristocrats.

No; it's evidence that some people will attempt to become that class of society, even after it's been abolished, so that they can have power over others.