It’s odd here in AU. It is opt-in, but I still (as the de facto partner) had to give final authorisation to go ahead with it. I don’t quite get it, and wish it was more respectful of the deceased.
It’s worth noting though that the process of saying yes and sorting that all out was in fact incredibly healing and cathartic for me. I wouldn’t necessarily think it’s a bad thing for grieving families to be involved in.
If you don't believe the state should be the defacto owner of your organs (I'd argue it's the recipient that ultimately ends up owning them, but whatever), then you can opt out.