How to differentiate between "has had" and "had"? eg.
1. He has had many affairs.
2. He had many affairs.

Although 1 uses present perfect tense, why it has been used at all? Isn't 2 sufficient to convey the message? Or is the usage in each different?

Similarly,
His wife divorced him because he had had an affair.
What's wrong with "he had an affair"?