Image via Wikipedia
Hardship is not necessarily a prerequisite for wisdom, but a wise mind can certainly benefit from hardship, just like it benefits from any kind of life experiences.
Any experience has its limitation. Experience itself does not bring wisdom. What makes wisdom is a capability of transcending experience, i.e. when facing hardship, one is able to keep hope and tranquil spirit hence overcomes misery; or when living an ordinary life, one is able to experience extraordinary hence goes beyond mediocrity.