Answer
A covalent bond has too much stability to be used in place of a noncovalent bond.
Work Step by Step
Macromolecules rely on their ability to associate and disassociate at will, as this ability influences how cells move and divide. This also allows the cells to control the transport of materials between organelles. As such, the bonds need to be noncovalent as covalent bonds would require a specific enzyme to break each bond every time the macromolecule had to disassociate.
