Of course, I don't really believe my plates and glasses are capable of feeling anything; it just lends an immediacy to the problem that the prospect of unexpected guests or a loudly disapproving boyfriend don't. Those people are adults, and they can deal with me however they see fit, but my dishes can't wash themselves. They're like helpless little dirty babies, and I've just been heartlessly neglecting them all this time. This sounds so dumb, and I want to make fun of it so badly, yet I now can't shake the feeling, despite every instinct yelling that this is some corny, superstitious bullshit.
I think this is due to something that's hardwired into the human brain.
We Have A Long History Of Treating Things Like People
Kondo didn't invent this idea; she's just tapping into it. So is Pixar, with their "Your toys are sad you abandoned them after puberty!" plots that can make even the most stoic of adults start ugly-crying in front of strangers. Musicians and sailors name their guitars and boats, referring to them as "her" and "she." Some soldiers name their guns and hold funerals for robots. Among those of you who own a Roomba, there is a certain percentage who feel bad if you accidentally kick it. Some of us curse at our cars if they don't start. ("You choose the day of MY JOB INTERVIEW to PULL THIS s**t?!")
It's a behavior that's been observed in humans since at least ancient Greece, and as long as it doesn't turn into an unhealthy compulsion (like, say, hoarding), it's fine. For example, the teddy bear you treated as a treasured companion was your way of transferring your dependence on your parents onto something else until you could be fully independent. In psychology, they're called transitional objects, and they're adopted more frequently by children who are in daycare full-time, i.e. children who are more likely to have separation anxiety. However, those children didn't exhibit any more behavioral disturbances than their peers.