Their parents willingly give the children into their care not unlike Catholic or Buddhist monasteries raising children given to them.

Only the kids are guaranteed to have a good life, the best education in the galaxy, have all their physical needs met, get to learn FUCKING SPACE MAGIC, and serve as important guardians of a galactic republic who don't even have to do cop stuff, unlike what the kind of idiot that accuses them of kidnapping children might say despite A CORE PLOT POINT of Phantom Menace being that the MOST REBELLIOUS JEDI MASTER WON'T EVEN STEAL A SLAVE CHILD