Adding egg yolks to homemade ice cream creates softer custard-like ice cream that freezes well and is easy to spoon out into dishes. Egg yolks serve as natural emulsifiers in the ice cream and help to mix the fats and water in the ingredients and reduce any fat/water separations.
The addition of egg yolks will also produce a richer taste, which many people enjoy; most homemade ice cream recipes call for four or more egg yolks depending on the amount of ice cream being made.