Why use both milk and cream in a waffle recipe?

I live in Europe and use a lot of European recipes. Here, traditional waffle recipes generally use a mixture of cream and milk as the liquid. The recipes include melted butter, so I don’t understand what the cream is doing. Any ideas?

Bocuse recipe for waffles (as an example) (found in Paul Bocuse "Die Neue Küche" Heyne Kochbücher 1976) – but representative of a great many traditional European recipes for dessert waffles.

• 500 g flour
• a pinch of baking powder
• a pinch of salt
• 1 tablespoon of sugar
• 250 ml milk
• 750 ml heavy cream
• 8 egg yolks
• 100 ml rum
• 300 g melted butter
• 4 egg whites

Is there a technical or chemical reason to use cream, even if you are already using butter?