you are not necessarily saving someone’s life. there is a possibility, but not necessarily. sometimes the organ is rejected, sometimes it is not transplanted in time etc
and lets say you were a health nut your whole life. took really good care of your body, you might not want to risk an alcoholic getting your liver and destroying it and then needing a whole other person’s liver. (or smoker, fast food lover, etc)
i find it slightly annoying that people “expect” everyone to be an organ donor.
so many people say things like “when it is your time, it is your time” or “god works in mysterious ways” but the second they are in an accident or get sick, it is not their time, it is time to get someone else’s organs.