Well, the simpe answer is, misunderstanding breeds fear. What we don't know makes us extremely uncomfortable. We ask questions like:

Is it bad or good?
What is the degree of bad or good?
If it is good, who is it good for? Same thing for bad.
Does it have monetary value? And if it does, I need to hoard it for myself.

And another 1000 other scenarios our wonderful mind can think up. Moreover, that is just your mind. Society also does its work to tell us what to think about what. Television, religion, parents, and friends all have part on how we view things. And they all say, everything needs it's nice little box with an even nicer rectangular label. That way, you can take comfort in knowing how to approach and manage this new thing.