You matter to people you don't even know notice you exist.
When I was a waitress I had a regular customer who always sat alone and ordered the same thing. He was friendly with sad eyes. I loved serving him even though I never got to know him.
One day I made him his usual out of habit and was surprised to find his booth empty. He killed himself. I cried for three months whenever anyone ordered that drink. I still wonder what I could have said to change his mind. I wonder if I missed a cry for help.
The point is I don’t think this man knew I would notice he was gone. I don’t think he knew I’d care. I don’t think he’d ever imagine that 16 years later it keeps me up at night that I didn’t save him. You have people who would surprise you by feeling your absence, by caring that you were in pain, by missing you long after you are gone.