As someone who mostly knows Bandori from the fandom and the PICO anime (and, thus, knows the characters pretty well but not necessarily their relationships), I have no idea why this ship is as popular as it is (as I've never seen them interact in canon yet), but I think it's pretty cute just imagining how it works. Like, from their personalities, I feel like they'd have good chemistry. So, I ship it, even if I don't understand why everyone else ships it too.