#1) The 60 million aborted babies are no longer in the actuarial for Social Security. New immigrants have to work at least 20 years to qualify for drawing on it for any retirement.
#2) Cheap labor which is rapidly deployable to needed areas. Flooding to meet labor needs in places Americans won't willingly relocate to.
Clean skin immigrants. Britain does this. They use immigrants that are untraceable for infiltration and covert intelligence tasks. They get caught and they didn't exist on public record. That is of enormous value to covert operations. No loose ends.
How many million agents do they need?