“First of all there are plenty of people who do kiruv krovim.”
The people who do kiruv krovim, do not do it “one on one” because there is no money for it. And for hopes of success for most kids who are at risk, even they will admit that “one on one” is the way to go. And most kiruv successes are those who are already curious about Judaism, not those who are totally not interested.