Why are shocks worse when you touch conductors rather than insulators?

 Conductors are materials that permit electrons to flow freely which means that they enable distribution of charge as a result of electron movement.
Insulators on the other hand are materials that impede the free flow of electrons. If charge is transferred to an insulator at a given location, the excess charge will remain at the initial location of charging.
That is the reason why shocks are worse when you touch conductors rather than insulators.