Does it justify the expense and the shortcomings though? Horses also have some advantages over tanks, like refueling from the grass on the roadside but they become mostly ceremonial anyway.

Yes, because AI is not good enough to fly a plane, detect an enemy craft, and react before a human pilot could. Like I said, they are developing UCAVs. They are not replacing all human-piloted strike planes, let alone all human-piloted air-superiority fighters, yet. Being able to pull a few more gs in a turn doesn't give you that much of an edge, yet.