This is also generally a selfish attitude where you personally benefit while structures that used to benefit society at large are eroded.

In that world, the vulnerability has more value to those who seek to exploit it for their own motives, regardless of the consequences. They hope that no one else stumbles on it and fixes it, preventing them from continuing to use it to do bad things.

In the world where it is disclosed, there is more value in fixing the vulnerability as the maintainer’s reputation is at risk (and potentially monetary loss or legal liability if they are shown to be negligent).