LLMs ironically are changing this[0], but at least until now, rifling through random people's data did not scale, so aside for a subset of cases where it was possible to automate access to some services or otherwise leverage them into a scam on the cheap, it wasn't of interest because there was literally nothing useful to do with it.

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[0] - LLMs, whether multimodal or combined with modern AI-driven STT / TTS pipeline, enable running highly personalized scams cheaply and in an automated fashion, which does scale up and suddenly makes this data important. But that's a very new consideration, one which passkeys were not designed for, because it literally was not possible or conceivable even few years ago.