Why was the 9th amendment added to the constitution and how has it impacted society?

The 9th Amendment was intended to provide a mode of interpretation for the Constitution, guaranteeing that federal courts would have been expressly forbidden from creating new governmental powers through clever interpretation. Given how much trouble varying interpretations of the Constitution have caused throughout American history, it's a shame this principle was not explicitly included. A lot of subsequent and continuing constitutional mischief could have been avoided.