It's not enough to know "what." The "what" has to make sense.
We don't always have the privilege of getting both in the same package. I usually have to be content with the "what" and somehow come up with patience while looking for the "why". If you're always able to get both at the same time I salute you. OTOH, you'd be foolish to reject the 'what' just because you didn't get both in one package.
Hey, a simple biology lesson would be "chickens lay eggs". Knowing which came first, the chicken or the egg, is a "why" situation that simply is not necessary to resolve in order for the student to understand who does the laying and what gets laid.