Why should B and C tax A for services B, C and D need?

I am not referring to corporate loopholes, those should be closed but neither party will touch that issue. B and C complain about their So-So security and Medicare that they need and poor (D) need, why not just tax themselves if they need it? A ('rich') doesn't need those. Why tax A so B and C can siphon some money then give what is left to D? Why even bother arguing fairness when you want to tax other peoples money then decide how someone else should spend it?