Noah pronounced the curse directly on Canaan because the cursing of Ham had the implications of a generational curse. Noah was not just going to be satisfied at seeing Ham suffer for his wrongdoing. He was so embittered and could only have pacified his anger in seeing a high range of calamity blazing down on not only Ham, but also on his seeds.

In the curse of Noah upon Canaan, he was not punishing him personally for something his father Ham had done. The words of Noah refer not to Canaan himself, but to the nation that would come from him. Ham had caused a breach between himself and his father that called for some type of judgment. The judgment would occur on his descendants.