Very simple. I am not a resource to be harvested. I find it interesting that they have changed the procedure to call it recovery now.
Recovery implies a type of ownership, something that was lost, has now been recovered.
My body, just like my money, my house, or any other possesions, is mine to determine with what is done with it once I have passed on.
I have no obligation to allow my money, my house, my posessions to be 'recovered' for the benefit of others. Now, if I wish to be altuistic, I can donate as I see fit, but i very much disagree with the attitude that not being an organ doner makes me somehow evil or horrible.
My attitude would be that if my immediate family needed an organ at the time of my death, it is theirs. I leave that resource to them. Failing that, I have no duty to provide, nor am I holding back some resource that belongs to the common good.