Why aren’t DNA test done automatically?

I’m sure a lot of you have heard stories of men taking care of a child that wasn’t even theirs. But they never knew. I’ve even seen stories where men paid child support for a child that they didn’t know it wasn’t their child.

I don’t think a woman should be offended by this either, cause it’s only fair. Plus it takes the burden off the man for asking for one. Cause it will come off as if he is implying she cheated. If it’s done automatically, everyone wins.