Some people say the question "why?" puts people on the defensive. "Why didn't you finish this project?", "Why are you like that?", "Why were you late?", "Why did you not do what I said?".
I some circumstances it does, but in others that question is very appropriate. "Why did you want to become a doctor?", "Why is the sky blue?", "Why do birds fly?", "Why are planets so far away?", "Why can't we breathe in space?". Why questions like that don't put people in defensive mode. It's all how you say it, I guess. Tone is very important.
The question "Why?" should be used appropiately to get a adequate response from the receiver of the message. "Why?" can open many doors for people and help people understand something that they previously didn't understand, and clarify something that didn't make sense to begin with. "Why read this?"
Challenge YOUR Life!