Most are in and about the world outside of the family. Groupings are not limited to children the same age. Classes are formed based on interest, not age, so the age spectrum is wide. Siblings join together to learn and play. Tolerance for differences is increased since exposure to differences is great.
Interaction goes beyond children.
Adults - neighbors, parents of friends, workers, etc. Not only do homeschoolers benefit from a wider age group than schooled counterparts, they also have more time in meaningful interactions. That is what socialization is all about. Socialization is simply the ability to get along with others, not just peers or fellow classmates, but others. Homeschooling is the perfect means for this.