Lying on DS-160 was the reason the Feds managed to initially arrest 9/11 attacker Zacarias Moussaoui [1]. It is significantly easier for cops to prove you lied to the US Government and detain/deport/ban you from entry if you're an alien than to try to prove criminal intent, etc. and that's why DS-160 has all those seemingly weird questions.
[1] <https://en.wikipedia.org/wiki/Zacarias_Moussaoui#Capture>