Why are the most abundant elements found in our bodies not the most abundant elements found in Earth's crust?

Why are the most abundant elements found in our bodies not the most abundant elements found in Earth's crust? (e.g., What characteristics of the most abundant elements in our bodies make them suitable for life?

How do the structures of carbohydrates, lipids, proteins (structural and enzymatic), and nucleic acids relate to their functions? Include in your discussion a brief description of the structure of each type of molecule