Because someone did it for you.
Two things people did for me in college. I was buying cleaning supplies I couldn’t afford, but could not stand the apartment anymore. The man in front of me was buying ice cream and flowers for his girlfriend and her daughter. He paid for my stuff too.
Second, at dinner with my girlfriends I was calculating how much I could eat. This couple walked by and the woman said, “you girls remind me of when I was your age; I’ll pay your bill up to what you have had now.” Thank god, we were all so poor….good people do exist.