I do know my blood type which is O+. This was because I used to race motocross and the racing license required yearly medical tests. I've had yearly tests for 26 years. In racing accidents, a known blood type can reduce the time cost in an emergency.
No, I never needed blood in my race accidents, but I did break my leg 4 times and my ribs twice.
Anyway, I didn't think it mattered much until a call came from a friend that had a brother in a car accident and needed blood urgently. He had the same blood type cos that was his brother. The hospital didn't have that blood in quantity. He needed Type O+, which I had. I called all my racing buddies cos I knew they would know as they also had to be tested to acquire race licenses. We found about 5 of them in 1 hour. We did call about a 100 people through the same race buddies who contacted other race buddies.
That day, a life was saved.