I feel like most of the replies to your comment talk about the technical aspect of it.

What’s stopping me is that I don’t have a mental model of the management of the passkeys for the whole lifecycle of my account. Can I use it cross platform? Can I allow someone else to use the same account? What happens if I lose or don’t have access to my phone or laptop? What if I die, can my spouse log in my accounts?

With username/password, it’s very clear what I need. I could write it on paper and give it to someone and it’d work. I feel more at risk of losing access to my accounts if I were to switch to passkeys, because I don’t fully grasp their long term lifecycle.