I have had moments of being out of control despite many many years of riding experience.
For example I took Lucas out on the trails planning to ride him to my house, there was one section of road it was about 200' at the most. He is fine with traffic, used to trucks and all that. However a bunch of motorcycles came up and were revving their engines. Lucas started to turn in the road, which is a section of road where the traffic is slowing for a light. I put my hand out to tell them to wait a second while I regained control and straightened him, the bikers ignored me and one passed. Lucas was sideways in the road after this so I put my hand out firmly to tell the rest to wait, they didn't and passed anyway. Lucas reared and tried to bolt. We were cantering on the spot a second.
Thankfully the other traffic stopped and I crossed through a parking lot rather than waiting for the intersections and so was back on the trail again.
So I understand that despite the experience level, things can happen. However an emergency dismount in this situation would have left my horse dead or very injured or just running through traffic and lost.
I did feel that if this had gone worse then my life could have been in danger as I was in traffic. However, his life would have been worse if I had just hopped off.
As a teenager I was on a horse that bolted, and kept going. I was seesawing her face and pulling the bridle hard one direction, and got nowhere. If I had just jumped off, who knows where that horse would have ended up.
To me it is just an odd concept, I would never fling the door open on the car I am driving and bail ship, I would try to minimize the accident as much as possible. It doesn't make sense to me that you would not do the same with a horse.
Clair, if a horse was on its knees I would just hop off, that is not the same as an emergency dismount to me.