In fact, they didn't. Their parents considered citizenship here so valuable that they stole it. And they had the use of it for quite a while, which nobody can take away from them, or even wants to. But we're a nation (almost as sovereign as Mexico . . .) and we have to protect our own citizens first—otherwise, we can't take care of others, either, because we won't exist.
If we let an infinite number of (for example) Mexicans or Guatemalans in permanently, we become the country they ran away from!
Julia Lynch’s parents never sought citizenship nor had any inclination to procure it, and yet Julia Lynch (born in the U.S. to them) never had her citizenship stripped from her after an 1844 court case.
Retroactively taking away citizenship (or saying they never had citizenship in the first place) would take away Julia Lynch’s citizenship and everyone else here that is 100 to 1 years old and had parents who are/were illegals.