Because sometimes I don't want to give it, and others won't give it to you!
If that person gives it to you, you can give it to him.
If I don't give it to you, you can give it to me.
But when you ask someone for something, if they don't give it to you, you don't want to give him anything.
Well, it's not good, but it's really embarrassing
If it's not expensive, just send something!
Although others always eat their share, it is really embarrassing not to give it, especially when others have already spoken.