I always ask "why?" because I really want to understand! It's not a defense mechanism, it's not being childish, it really is all about trying to get to the deeper meaning of things. I do a lot of root cause analysis at work, and one of the most important tools is to keep asking why until you've found the true root cause of the problem...you can't fix it if you don't know the true cause. I tend to apply that to my life as well. Additionally, I'm just really curious and like to learn things.

I know that some people find "why?" annoying, so I've started reframing it to "Can you help me understand the reason behind..." That makes it sound less like I'm just not accepting the answer and more like I want help to understand the deeper meaning (which is truly what I want).

Sometimes, I think people find "why" annoying because they don't have the answer to the question but don't want to admit it. If I ask why and someone doesn't know, I'd rather they just admit it...and then offer to explore the answer with me! I'm never trying to be difficult when I ask.