I would think very few green-card holders would be interested. Most of them are in professional jobs.
At any one time there are 15 million green card holders in the US. We take in 1.1 million legal permanent immigrants every year. They are all issued green cards. After five years, they can apply for naturalization. 20% of the legal permanent immigrants we bring in annually lack even a high school diploma. The vast majority of green card holders are not professionals.