Humans are funny things, they love to argue over things; they also love to try and order and quantity things. Every day billions is spent on arguing with money which is the better football or singer by comparison. It is what humans do to justify their curiosity of things.
Those bits of space junk have been out there for millennia, it made no difference to Earth until a huge one visited destruction on the Dinosaurs by rapid climate change as it exploded into the Gulf of Mexico.
Who ever is the boss with the most respect or power decides, someone disliked Pluto and wrote a set of arbitary rules to make a Planet a Plutooid = (dwarf planet).
If some sponsor decides to donate a million dollars toward the upcare of the ISS on condition that Pluto is REmade into PLANET status, then Pluto will soon be the ninth planet again.
Money and egos and power as prestige alter how we view the world and our Solar System. I would love to have seen what the Voyager space bots have seen . . .