Actually, child slaves in that part of the world are often used for agricultural labor, and as indicated by this case, forced street-begging is also common (though this was a sting, the plan described was obviously quite believable to the sellers). Girls are more likely than boys to end up in brothels (though of course quite a few boys do too), and I would think form the majority of domestic slaves too (after all, these people routinely treat their wives and daughters as households slaves). And some boys up as camel jockeys in various Arab countries, beaten into cooperation and starved so that they won't gain weight and slow the down the camels they ride in the races.
Technology scores! Camel Jockeys are being replaced by robots. "Doing jobs that Christians won't do!"
PRETTY BOYS -Afghani Wedding Singers Are the Sweetest Plum (Vice Magazine Immersion Issue v12-no10 2006)
But some old warriors can’t help themselves. A 2004 report on human trafficking by the International Organization for Migration notes a trend of gunmen sexually abusing boys. Although Afghani law prohibits homosexuality and pedophilia, neither crime qualifies for the far more unacceptable charges of adultery or pre-marital sex.For the incorrigible pederasts, there are wedding singers—fairylike boys, some pre-pubescent, who cover nationalist anthems and local pop songs over tablas and synthesizers. Demand for them at weddings is huge. But wedding singers are scorned on the street and minded closely by their families or managers. Numbering in the hundreds in Kabul alone, they are considered the catamite class.