It is after all an established fact that once one's cultivation base gets destroyed, it can never be restored. There are no such doctors in their empire who can perform a miracle of mending one's cultivation base nor did they know about any treasures that could do so.
As such, it was for his own good that the boy gives up on any foolish ideas or hopes he still had about becoming a practitioner and cultivate once again.
That said, how could it be so easy for someone who had been cultivating battle energy since a very young age, to suddenly accept the reality and give up on their dreams? It was no different than giving up hope.
It would be impossible for anyone, and it was the same for Lin Dan who came from one of the three prestigious clans of the Cloud City and was raised as a genius by his clan.