I became a blood donor mainly due to one event in my life. I was at the Emergency Department of Middlemore Hospital with an in-law's affliction, when an accident victim was brought in. He was covered in blood, bleeding and in severe pain and probably shock. The receptionist called up to the Blood Bank and requested volumes of a certain type.
When she was free, she told me about donating blood and how my blood could save 3 lives. I donated the next day and have been all my life. That was 30 years ago and 41 times (of donating) ago.