I can't speak for everyone who is like this, however, I can speak from experience and let you know a possible cause.

Perhaps, the people want to feel useful to you. They possibly have some kind of deep seeded issue or insecurity of some type that makes it to where they feel the need to be useful or go out of their way to help you. Perhaps they think that if they don't help you, you will abandon them.

I know because I'm like this to some extent. While I don't get angry with people for not letting me help them with something, if I'm around friends or people that I like, I tend to go out of my way to help them with whatever that I feel I need to because I want to be useful to people so they have no reason to betray me later down the road. I work to try to be the most ideal perfect person to people that I care about because I feel that if I let any of my weaknesses or flaws through the cracks and others see that I'm not strong, smart, or good enough, that they will not want to hang out with me or stop caring about me.

Perhaps their reasons are similar to mine?