A total ban would have to go hand-in-hand with eliminating all the gibs. The only reason the destitute keep popping out children is because the government gives them money for doing so.

If you look into the Gosnell abortion mill incident that happened a number of years ago, there was a theory/rumor that the Feds were paying single mothers up to a certain amount of children, and then after that they would get nothing extra. So some of these women were going to abortion mills because not only they couldn't keep their legs closed and were absolute morons, they had just enough sense to know that no additional gibs would be doled out.

The Left are trying to keep a certain population size of them so they continue to be a problem for the rest of America, but they don't want the problem to cause a descent into chaos.