The more offenses someone commits, the more likely they'll make a mistake committing one of them and get caught. Yeah most money launderers will have no moral qualms about lying on a form, but someone already on the fence might be dissuaded if the risk of getting convicted increases.
Or even if consciously criminal then one would want to minimize risk of getting discovered.
If the criminals risk forfeiting their money they may look to other avenues instead of using American shell companies.
I very much doubt anyone is under the illusion that this will stop criminals trying to launder money through American companies, it just makes it easier to seize assets of potential laundering operations and to investigate sources.
Also, finding an attorney that is willing to lie, is very easy. How do you think all this stuff is already happening illegally now? ;)