Why should I pay child support when she has income support already?

i have friend who had 10 year old boy and she claim CSA about boy father have’nt see or paid him for last 4 year.So CSA say sorry they cant do cos she got income support used this for.But shock me my ex have massive income support, Child tax credit, Child benefit, DLA(Disabled Living Allowance)and SDA(Service Disabled Allowance.

That all 5 benefit she got also inclued CSA. WHY THAT? Why i should pay her CSA as she got income support.