Why does an insulator has a high resistance

Sometimes it's easier to think of electrical conductance. Conductance is the opposite of resistance. It's measured in mhos. Conductors conduct electricity well. They have high conductance. Insulators don't conduct very well. They have low conductance. Because resistance is the inverse of conductance, high conductance means low resistance and vice versa. Conductors conduct electricity well. They have high conductance and low resistance. Insulators don't conduct very well. They have low conductance and high resistance. This come from my book Conceptual Physics 11th edition by Paul G. Hewitt Pearson