Why?

Why is it that the word 'why', when used in an interrogative sense is taken to have all sorts of meanings and connotations than the one which is the most straightforward? Here is an exampe:

Someone: "People feel like eating less in the summers."
Me: "Why?"

Now either the answer should be "Because ... xyz (I don't know myself so can't tell, something to do with metabolism maybe)" or "I don't know".

But of course, the answers you do end up getting make you wonder whether its yet time for us, as a race to think about AI or just invest in discovering natural intelligence first.

I wonder why asking 'why' is discouraged. Actually, asking anything seems to be discouraged. I've been told innumerable times to stop asking silly questions. Now I'm not quite sure whether the question was silly or the people who I asked were.
But I have to sadly end up drawing the following inferences -
1. People don't want to let others know that they don't know by saying "I don't know"
2. People don't want to let others know that they don't know by asking questions.
3. Such people would rather not know than let others know that they don't know.
4. Such people don't want to know or learn.

I rest my case :P