Why are seven old people seven?

Seven old people is the highest number, and people think that seven old people symbolize the seven deadly sins in Catholicism.

1, excerpt: Think about these seven hideous monsters. Although they are so old, they have immortal charm. If I see the eighth cold, cynical, resigned incarnation, the annoying phoenix bird that combines father and son, it won't kill me.

2. Seven Old Men was given to Hugo by Baudelaire, a pioneer of French symbolism and symbolism theory. His creative idea of "taking ugliness as beauty" influenced many later symbolist poets. Hugo, on the other hand, is a master of French romanticism and the most faithful believer of "humanitarianism". During their life, France in the19th century kept changing its style, but both of them paid attention to the people at the bottom of Paris at the same time and fully expressed their inner feelings in the form of "poems". Under their different creative techniques, they have different "Parisian styles" and responded.