The problem with such a high ranking in his souls lies within his reincarnation. His current life is SSS ranked but his soul climbs the rankings even further. The creator god can not do everything so he wants to kill the MC early to before he gets too powerful in his next life (where his memories would be deleted and everything could happen. Even if he was a pure soul before anything could change his way of living. Lets say he reincarnates as SSSS human and lifes a grand life. Then some S rank soul person chases after his wife / sister or whatever and ended up killing her. This powerful SSSS rank human could ruin the balance of the world for a very long time.)

To avoid it the MC starts to focus on his own wishes a bit more by dating, spending money and so on. He invests his money for things he desires without causing harm or helping too many people. That backfires later on and he accumulates another ton of good deeds = high soulrank.

In a chanel where we talked about the novel alot we realised that this is actually a plothole. The MC ignores the balance of the world and disrupts it heavily thus he does evil things caused by his virtous desire. The intention is good but the method is wrong. At one time he creates fake bodies for many people and transfers their souls into them to help them fix the soulranking. This is like a bigbrain lawyer using any means possible to safe a criminal. Its bad bad :D