Meh, you're looking at it very idealistically, instead of realistically. It's very obvious why no one wants to deal with party recruitments just to have the other players(s) open a damn door at the very start of an instance, when there's nothing else that encourages party play in the instance. Not to mention how the rewards heavily discourage making parties. It's just wrong to blame the playerbase on this one, anyone can see why this is a terrible way to make an instance party-based and why it fails to convince even a single player to make real parties to clear the instance.
If gravity designed it this way, it's only because there is no master account system in kRO. There's no other reason why they wouldn't make the requirement 2+ "real" players to actually enforce having parties if that was their aim. But we do have the master account system, so why not utilize it? What baffles me is that you're also not a fan of such custom changes that would actually enforce party play as well. Instead you just insist on keeping things vanilla when the implementation is obviously terible and has a 0% success rate on accomplishing what it's supposed to do, just for "principles". Okay I guess, but it just seems futile to me.