Horses see us without perceiving us while still being social animals who can bond with us, and they can represent so many different things to us culturally (freedom, wildness, independence, luxury, sustenance, masculinity, femininity) depending on place and time. They're this wonderful balance of beautiful, powerful, fragile, and awkward, and I think those kinds of contradictory dichotomies hold a lot of appeal for us as a community. There's just a lot of material to mine out of horses.
I'm really glad you enjoyed the game!