That's the thing, of course. "Why" is the instrumental case of "what" and implies an actor, agent, or motive.
Scientists don't waste much time on "why." Simply finding "what" or "how" is enough to keep one busy.
I found the following on the net:
1. Material cause, or the elements out of which an object is created;The development of potentiality to actuality is one of the most important aspects of Aristotle's philosophy. It was intended to solve the difficulties which earlier thinkers had raised with reference to the beginnings of existence and the relations of the one and many. The actual vs. potential state of things is explained in terms of the causes which act on things. There are four causes:
2. Efficient cause, or the means by which it is created;
3. Formal cause, or the expression of what it is;
4. Final cause, or the end for which it is.
It seems to me that science concerns itself with the first two "whys", philosophy/religion with the second two.