All the bakers in my life tell me that the proportions of ingredients are crucial to a successful outcome due to the chemistry involved, much more so than with meats and vegetables and asphalt and such.
Same thing holds true for the mixing and the oven temp and the pan-greasing and all that...even things like altitude and humidity come into play. It's one giant ongoing chemical reaction, baking is. Of course, all cooking is to one extent or another, but there are people who bake well, people who cook well, and not all that many who do both equally well. It's a knack!
That's just what they tell me, though. It might be one giant chain-yank, but it seems logical on the surface, the whole "chemistry" thing. I mean, you start throwing around with stuff like baking powder, you got some science class stuff right off the bat!