When related to personal questions is "I don't know" only a euphemisms for "I never bothered to think abou it"?

"So why did you do this?" - "I don't know"
"Why did you cheat on me?" - "I don't know"
"Why do you feel so angry?" - "I don't know"

Ugh. A lil bit of self-reflection can go a long way, folks!