(Im taking this thread as a learning experience, since i dont know)
Ok. It would be "fair" but it wouldnt be "right" why should Person A give up part of his money and just throw it away to Person C without Person C equally contributing. In other words, why should Person C get money for doing nothing
Call it equal opportunity, or close to equal opportunity. If Person C can afford a decent life in a decent house with a decent nearby school, Person C can send his children to the decent school and possibly university if they're intelligent enough so that the children can develop into Person Bs. Who knows how many intellectuals, inventors and such the world has missed out on because they weren't born into the right social class.
I think the main thing about socialism is that some people are more focused on their own progression and success while others are more focused on the community's progression and success.