Because removing Section 230 would not do anything to address the concern of the person saying it needs removing! It is a shield against civil liability, not criminal liability. If Facebook are aiding and abetting to profit from criminal fraud, Section 230 does not allow them to skate free, and so, it does not need to be changed.

If Section 230 were gone tomorrow, it would likely only be the Facebooks of the world who would survive, as only they could afford the lawyers necessary to fend off frivolous lawsuits. No sane person would run a free web forum where they agree to accept the liability of being a “publisher” for anything some rando posts.

Certainly I think there is a case that could be argued that when a web site says they explicitly screen and approve every piece of content, which as far as I know is what these ad tech companies claim to do, that does create a duty of care which is not present for automatically approved UGC. But I’m not aware of anyone in particular arguing this. Certainly that would be the thing to do first. Otherwise you are advocating for solving a cockroach infestation by dropping a nuclear bomb on the city.