The so-called courage under the promise of great reward meant that with such a powerful incentive, it wasn't just the offspring of those families who were tempted. Even those brilliant martial artists from sects and clans considered their options.
Certainly, their sects had been generous to them, but even if those sects were exceptionally powerful, the most they could do was to train them up to the Mythical Realm, and that too was a matter for several decades later.
However, joining Zhang Menglong's school meant that the Mythical Realm was just a starting point. Perhaps they might even touch upon the legendary Heavenly Human Realm. At that point, what would their own sect mean? They would have to be extremely respectful to them, even if it meant betraying their sect.
"Bastard, our sect has nurtured you for over a decade. Is this how you repay us?"