Noah stopped asking questions after Ana's reply. The truth was that he still thought like a lone cultivator. He had a few people that he cared about, some even deeply, but he was still unable to see his organization's well-being over his.
Instead, the cultivators of the hidden world were different. The new generations were slaves since birth, and they had lived through a pain shared by all their peers.
Moreover, escaping the summoning and obtaining the power to travel through the sea of magma wasn't easy, especially in their condition. The natives passed down their techniques orally, which strengthened their connection with those in a similar situation.
If cultivators were to leave in mass, that world would soon be devoid of cultivators. There would only be commoners with no chances to cultivate, and those who had benefited from that system didn't want to leave them in that state.