Question

Electrical switches are made of plastic

Answer 1

yup
to avoid the flow of electricity in person while switching on

Answer 2

If we have to give reason then here is the answer.
Electrical switches are made up of plastic because , plastic is a good insulator of electricity and it doesn't allows the electricity flowing inside the switch or wire to be flown out .Cause if we allow it to flow outside also then a person near the switch or wire can get shocked.