since wi is a 50/50 no fault state. When a spouse is remarried why don't they take into account that income to lower child support payed by other parent.

Because it is the responsibility of the biological parents to support their children not stepparents, at least that is how the courts see it.

Here's another reason- if the NCP is allowed to pay lower support because the CP is married, then it would also allow a CP to get HIGHER support because the NCP is married. In other words, what applies to one parent, applies to both parents.
Xena

left this out its also a shared custody 50/50. Same costs as children switch between families weekly. Why not go by household income. Now you have a father paying child support to a family that's household income is twice his. He still has the exact same costs.

left this out its also a shared custody 50/50. Same costs as children switch between families weekly. Why not go by household income. Now you have a father paying child support to a family that's household income is twice his. He still has the exact same costs.
It doesn't matter what the HOUSEHOLD incomes are. The only thing that matters is what each LEGAL/BIOLOGICAL parents' incomes are. In the case you are referring to the father is earning more than the mother.
Xena