Organ donation is a long and incredibly difficult process. It can be very difficult to get on an organ donation list, and they may not get the organs they need due to the short supply. People can only donate a few organs while they are still alive, so organ donation after death can be extremely helpful for sick people with conditions like heart defects.
There is also the issue of getting a compatible organ. You have to get an organ that matches with your body in order to get the transplant. There is no guarantee that the one organ available will be compatible with a person. Even a blood relative might not have an organ that is compatible. So the more people who become organ donors, the better the chance there is for another person to live.
Organ donors do not have to be the healthiest individuals; anyone can donate parts of their body even if other parts are not in the best shape. A heavy smoker could still donate something like their eyes or even the bones after their death. Every part of the human body can potentially be used to help a person in need. The skin, for example, can be used to help burn victims if doctors get to the deceased fast enough.
In your will, or by proxy after you die, you can still dictate what parts of your body are available for use. If a person wishes to hold on to specific parts of their body, they can. An organ donor still has a certain level of control over their body.
The community still needs organ donors; they are in great demand. While scientists are working toward creating organs in labs to help save lives, they have not yet reached a point where they can keep up with the demand of organs.