Horses are kind of the most unfuckable animal girl.
Like that's a cute girl, but a horse's main, ears, and tail are not the first thing I think of when I see a horse, more like their long, ridable backs, and shape. I don't see a horse girl and see an immedieate connection to me riding her, which would be fun and sexual. Like it would be sweet if she offered me piggy back ride, but she doesn't have any extra body parts of muscles that would let her gallop while I ride on her back. Not like a Kangaroo girl or something where you could realistic put your face in her pouch you know?
Like I'm not huge into fur, so for me an animal girl's whole draw is how her animal instincts affect her as a person so a Catgirl is just aight, but the DEEP seated instincts that make her want to scratch, lick herself, sleep, be independent, be clingy, be fickle. THAT'S Attractive, and I just don't see any of that in horse girls.
I don't even see any humanity in horses. Their eyes are one of the most soulless things in the animal kingdom, about on par with a fly's. Absolute no humanity behind them. Maybe their ancestors had souls and us as humans bred it out of them, but we've turned them into pure tools.
Like guys I watched like the first five seasons of my little pony and I never once wanted to fuck one of them, despite the billion times Applejack impressed me. It wasn't until the human high school AU did I want to fuck em and they had no tails, ears, and just looked like Bratz dolls. Horse girls just ain't for me.