^Sometimes asking "Why?" once isn't enough. 5 times usually is.
The Toyota company figured out that "5 Why's" is usually enough to get to the real reason behind something. It's not that people are lying – but it forces them to think deeper. You can do more of them – or less – but five times in a row usually seems to be enough. Note: Remind me not to work for Toyota. This would get annoying
"The vehicle will not start. (the problem)
Why? – The battery is dead. (first why)
Why? – The alternator is not functioning. (second why)
Why? – The alternator belt has broken. (third why)
Why? – The alternator belt was well beyond its useful service life and not replaced. (fourth why)
Why? – The vehicle was not maintained according to the recommended service schedule. (fifth why, a root cause)"