Please explain to me how a paternity test catches a cheater that is none other than the mother?

It's true it can only catch the mother, but so what? What's your point? Of course it only has the possibility to catch the mother, but it's only fathers who are in danger of getting cucked to begin with i.e. being tricked into raising a bastard child as their own. Mothers don't face that risk. If the baby comes out of her, she knows it's hers lol. What would even be the point of protecting women from something they aren't even threatened by?