Because most of the world does not have the infrastructure that the US has, and so they wouldn't be able to benefit society (as a whole) nearly as much. Becaus

Because most of the world does not have the infrastructure that the US has, and so they wouldn't be able to benefit society (as a whole) nearly as much. Because some people are queer or from other minority communities within their home country (e.g. Dalit in India), and would be subject to discrimination, including and up to murder, in their home countries. Asylum only covers the most extreme cases and not the day-to-day discrimination that minorities face worldwide. Because freedom of movement is an inalienable right that comes with being a human, and borders are inherently oppressive. Because most of the world is a harsh, dangerous place, and supporting the decisions individuals have made to stay or get out, given the circumstances they're in, is inherently a moral good.