I've fallen off more from poorly fitting saddles than any other reason I think!
I've found, in general, if the saddle is a good fit, I stay on. But I've had saddles that were not-a-good-fit roll onto the side of the horse when the horse spooked.
I've done a couple "emergency dismounts" where I've baled on purpose, but have only truly been bucked off once.
I was actually bucked off by my very best horse and it was totally my fault. I was cantering him around some trees and all of a sudden there was a bush in the way I didn't realize was there. He jumped it, I lost a stirrup, and he started bucking. I stayed on for a couple of bucks and then hit the ground rolling and ended up on my knees, perfectly fine with no bruises or anything! And I was so shocked I went up to my horse and asked him if he was okay, lol!
I think my hardest landings have come from when I was younger and rode bareback. I don't "do" bareback anymore!
I've been riding 17 years.