Abortions choices and child support

Just curious on the view of this, if you have a 1 night stand and end up pregnant.

The guy wants you to have an abortion and wants nothing to do with a child you don't and get child support from him for the next 18 years.

Now let's reverse that, same situation except the guy wants you to have the baby, even offers to take full custody of the child after it is born and you abort the pregnancy.

So my point is, if a guy wants nothing to do with an accidental baby, why should he have to pay child support if you decide not to abort?