We aren’t doing it already because the Bad People have power and if we did it, it would frustrate their Evil (or at least Morally Suspect) Purposes. Frustrating such purposes doesn’t count as a downside. Depending on who you are talking to, taking money from rich people, allowing people who make stupid choices to die, or preventing foreigners who want to from entering your country isn’t just a bad thing that’s outweighed by its good consequences; it simply doesn’t warrant an entry in the “costs” column at all.
We aren’t doing it already because the Bad People have power and if we did it, it would frustrate their Evil (or at least Morally Suspect) Purposes. Frustrating such purposes doesn’t count as a downside. Depending on who you are talking to, taking money from rich people, allowing people who make stupid choices to die, or preventing foreigners who want to from entering your country isn’t just a bad thing that’s outweighed by its good consequences; it simply doesn’t warrant an entry in the “costs” column at all.