Aegon had once wondered about the importance of Affinities if Runes did all the work, but he soon found out exactly why they were so crucial.
Affinities played a huge role in the conversation. If Aegon had to describe it, it would be like talking to a family member or someone you were very familiar with, someone you shared a close bond with.
Those people would understand you even if you didn't use perfect language. They would also be more willing to help you and would cooperate far better than a hostile stranger ever would.
Affinities acted as that close connection, except instead of people, they connected you to the laws of the world.
If someone had an Affinity with Fire and tried to use Fire-based spells, they would have a much easier time casting them than using other elemental spells.
The power they received from the world would be greater, and the resistance from the laws would also be weaker because those very laws were willingly allowing themselves to be used.
