Found a bunch of horses, gathered them up, etc,
But when I get on them to tame them, no hearts show up, and none of them try to kick me off or anything. I tried feeding them apples to raise their temper, but it didn't appear to do anything. After getting frustrated from trying so hard, I just summoned one in already tamed with the /summon command, got on it, put on a saddle, and it STILL wouldn't let me ride it around.

After looking up answers, I couldn't find anything, except for one small post over on Reddit that remained unnoticed. Turns out it's because of the new "passengers" tag. I heard it's like this for pigs too.