Napoleon almost always attacked. He was a great believer in the attacker's power to decide the time, place, and other circumstances of battle. The defender must accept battle on the attacker's terms. Napoleon always prefered to control the battle through the use of offensive action. For Napoleon to surrender the initiative and let Wellington attack him would have been out of character. It also would have allowed Wellington to wait for Blucher to reinforce him.
Because that's what he did. He was the agressor, the invader. That's why Wellington had marked the site long before. He knew he'd be fighting a defensive battle against a French attack. He didn't know the Prussians would be defeated when he planned it.
Agreed. Here is a website that has some of Napoleon's quotes on Warfare: The Words of Napoleon and Others Who May Have Influenced His Methods
It is very noticeable how strong an emphasis he puts on aggression and offense.