What kind of person would even want to falsify/lie throughout the clearance process. It's such a long and arduous process and the payoff is basically nothing. If it's actually an illegal trying to get into the system, they'd be better off going into politics where you gain automatic 'need to know' and have no repercussions for lying.
The forms are just materials they lean on during your security interviews. They kind of want you to lie about something to give them fodder to yell/break you. You're not going to prison for lying on your SF86. The polygraph hasn't even caught a traitor, they're all tools for breaking people