The cartels have long used kids as their drug runners. They would recruit and even kidnap local kids, sometimes tourists and either entice them with large payouts or simply force them to run the drugs acorss the border. Recently however, cartels have begun to kidnap American kids from Texas borders towns along the Rio Grande River.
For the cartels, kids are cheap and expendable drug runners. If they are captured or killed while smuggling, the cartels will simply replace them with other kids.