I've had four concussions and because of that, it takes the simplest fall to create another one. I do not get on a horse and often where a helmet when around the youngsters now.
Last unplanned discount happened on a green filly that scared herself, we were in the arena with a soft landing. I got only a mild concussion, but the helmet was damaged on inside, so I know it would have meant a hospital stay rather than trip. Cracked ribs, huge bruise, mild concussion was it.
First concussion was trying to catch a young stud colt while on medication. Got halter caught in foot and flipped over backwards...ended up severe concussion and in hospital for a couple of days. Next one was taking a photo of a new foal a couple days old at dusk. Caused the flash to go off and the mare attacked the camera I was holding, knocking me off my feet, hitting our hard ground and again, another concussion. So you don't have to be "on" a horse to get a concussion....a helmet would have saved me both times.
Lastly, I'm excited that my photo of myself and my Morgan mare Ayla on a rock in Monument Valley a couple years ago is now being used in a national ad campaign for the riding program Pathways. It is finally getting accepted to be wearing a helmet while riding in "full" western gear/attire. I swear by wearing a helmet and now have my husband wearing one.