Selfish people would simply not care. But I know many caring and civic-minded people who have never donated blood. Why?
Some are too busy. In reality it does not take a lot of time. The actual process of donation takes only 6 to 10 minutes. Even including the preparation and the post-donation rest, it requires only 40 minutes to an hour.
Some are concerned that they might get infected by some disease. In fact, a new sterile needle is used for each donor, and it is discarded afterwards. So there is no chance of getting infected with anything.
Some are concerned it might be harmful for the body. Roughly one-tenth of the total volume of blood is taken. That volume is made up in 24 hours, and the human body soon makes up the the lost cells. Many people donate three to four times a year regularly. Some of them even run in marathons in between. They are fitter than most people their age.
Some feel they are too young, too old, too fat, too thin, too weak, or too unfit to donate. There might be some truth to that for some people. The easiest thing to find out is to give it a try. They check your age, weight, iron level, blood pressure, and certain risk factors before taking your blood. And to be sure, you can check with your doctor first.
Some are simply squeamish about the sight of blood. That, like other phobias, can be overcome if there is a will. Just imagine it is your loved one at the receiving end. Would you be able to overcome the squeamishness? Surely you would.