When someone asks you why you like or dislike something, or why you want or don't want something,

I am, as they say, a grown-ass man. I owe no one any explanation for my preferences. 

It is what it is, deal with it. 

You asking does not obligate me to answer.  I might just walk away or hang up on you, or I might say noneya.

Talk to the hand as you'll most likely get more sense out of wit    :) 

It would depend on the context. In general, I will give some sort of explanation unless I have a good reason, such as it's too personal or the person asking is being obnoxious. If people are curious or what to know me better, I see no point in being rude.

  I agree with Jane‘s answer above: it depends entirely on the situation. For example, my wife asked me why I didn’t like the meal she had prepared. I was honest with her and told her why. It was no skin off of my back, so I did it, no big deal. A coworker asked me why I don’t like cold weather, because he loves it and can’t understand why some people do not.  I didn’t go into any detail, I just derailed the conversation by saying that I prefer hot weather. He insisted on knowing why, I told him that there was no way either of us would change his mind about it, and that there wasn‘t any answer I could give that would satisfy him, so it was useless to even discuss it. People who can’t see beyond the concept of personal choice, what can I say?

~

It all depends on who's asking and why.  If I'm passionate about something, I might try to explain why.  But if someone is just grilling me to be nosy, I don't feel a need to explain.