The discipline of mechanics, whether classical or quantum, is very much in the business of telling us how things happen. When I apply a force to a ball by kicking it I “cause” the ball to accelerate in a mechanistic way, and if someone asks me “how” I made the ball accelerate I can honestly respond “by kicking it.” This is how we would normally render Newton’s second law, f=ma, into language: A force causes a mass to accelerate...so I applied a force with my foot and off the thing went. (Note that it's rather odd to render an equal sign as "cause," but this is how it is generally interpreted at any rate.) Of course, this is not an adequate response to the question of why I kicked the ball and we don’t expect mechanics to answer this question. With this rough distinction between mechanistic how’s and purposive why’s in mind, we come to a platitude repeated in high school courses that I truly despise: Science tells us how things happen, but it requires religion, philosophy, or some form of ethics to discuss why things happen.
I have no idea what does or does not require philosophy, but the assertion about science is only true if we restrict “science” to the disciplines of classical and quantum mechanics. But this is not even all of physics, much less all of science! As I hope you will come to understand, the laws of thermodynamics are about why things happen naturally or, to use the jargon, spontaneously. For the time being suffice it to say that if they explain anything, they explain why a process occurs because they certainly don't explain how anything happens. This is why thermodynamics and mechanics evolved as distinct disciplines until their unification through statistical mechanics (more about this in later posts) and also why mechanics does not deal explicitly with time-directed, irreversible processes.
So “science” has never been in the business of avoiding questions about why things happen and it should not avoid them because its real job is to provide adequate explanations of natural phenomena. Nothing that leaves one with no understanding of why a process occurs could be an adequate explanation. However, biology and the theory of evolution in particular, as I wrote about before, have been particularly damaged by this view that “science” must restrict itself to providing only mechanistic “hows.” In fact, while I’m digressing, in case you haven’t figured it out by now, I don’t believe in Science as such at all. There are only the myriad things people do and measure under more or less controlled conditions in more or less clever or technical ways with concepts that are more or less quantifiable. People who invoke the spirit of Science with a capital S (White lab coats on white males and “pure facts” rendered in the antiseptic UV light of enlightenment reason) most often merely wish to claim blanket authority for ideas which, in the spirit of science, ought to stand on their own.