Chill, PR. Organ donation is a personal thing as it involves that person's organs, not your's. There are plenty of reasons to donate and there are plenty of reasons to not donate. There is no need to make excuses about a body you no longer need; so these are reasons, not excuses.
One I hear sometimes is the fear that if someone related to a medical professional needs one of my organs, will they let me die to get it? That's probably one too many Law & Order episodes talking, but there you go.
I looked on my driver's license and it doesn't say organ donor, but I thought that I had agreed to do that a long time ago.