I believe it has to do with the complexity of math and music. When we start with mathematics we begin with simple statements like "1 + 1 = 2". However, the older we get, we learn more abstract and complicated forms of mathematics. We learn Geometry, Algebra, Calculus, and other "difficult" forms of mathematics.
The same is true of music. We learn notes at the beginning when we study it. We slowly learn how to put those notes together to make a "song." We then understand more as we study further into music. Eventually, we learn how to form a symphony.
In the same way, as we live, we progress slowly. We learn how to use our hands to grab things. We then progress further and we use all our limbs to walk, run, and to do other things. We learn how to speak and communicate with others. We then begin to understand other parts of life as we age.
Throughout life we change how we perceive the world. We learn there are other cultures that have existed and exist now that are different from our own culture. We learn to see value in the things outside of our own small internal world that we had as a child. Like a flower, we open up and see the world differently.
Without this process of growing up, we cannot truly experience what life is. It is only as we age and learn that we can understand how life can be truly lived.