When you own multiples of a thing it’s natural to want to name each one. Especially things as personal as musical instruments.
I mean, that's not my instinct, but I don't think there's anything wrong with it. I'm not at all saying people shouldn't do it. I do think that if I were to name mine, the urge would be greater with a smaller collection and less so with a larger collection. Like nearly everything, individual ukes tend to become less special when someone owns many.
I'm mostly just curious if people who name their ukes are doing it for the sake of referencing them in conversation, as that seems to be one of main reasons people name things. The only other reason that comes to mind is for sentiment. And while I'm sentimental enough that I've been teased for it, and I think names are a special thing, and I love my ukes, I guess I haven't really had any urge to name them.