Why is it important to know if a covalent bond is polar or nonpolar?

Polar Covalent; the result is a bond where the electron pair is displaced toward the more electronegative atom. This atom then obtains a partial-negative charge while the less electronegative atom has a partial-positive charge. This separation of charge or bond dipole.

The dipoles create dipole dipole interactions which are inter-molecular interactions and thus effects the reactions it takes place.

Also Polar dissolve in water and Non Polar don't.