If you are the horses' food provider, you stand a much higher chance of having them come when called. Not my case, so they don't always come. They look up and look at me and think about it. And maybe they come. Maybe they don't. But I am getting more coming than not lately.
My dad is the main feeder for my horses and Scars won't give him a second glance if he doesn't have food lol. But Scars always knows it me because I jump down the steps and yell her name and I always get an answer from her and my by the time I get to the gate she's pacing the gate nickering at me. Posted via Mobile Device
I don't put a whole lot of though into the "why not" of a horse not coming.
I do the night feed at the barn and every night I go out to the pasture and yell for the horses. Same time, same food.... sometimes they come, sometimes they don't. I yell louder, call them names, threaten to turn them into Alpo and then they'll sloooowly wander on up and then practically trample me because OMG, she's here with lead ropes and that means FOOD!
Who knows... I just lump it all in with things like the pony who never seems to figure out that to go eat dinner he has to walk around the gate and into his stall. Nope, gets stuck on the backside of the gate every... single... night.
Now my horse is ALWAYS ready to go it. I never call him, he's jumping up and down at the gate because not only is dinner ready, all the other horses are inside and he's ALONE!! (he goes in last).