Personally, I think riders under 12 should where a body protector at all times and riders under the age of 18 should where them competing and if jumping high or XC or hunting but after the age of 18 it your decision X
I'm not against protection but I'm not exactly for it either.
Body protection, including the use of helmets and body protectors make many riders believe they can do anything on the back of a horse and not risk injury. The amount of times I've personally seen mainly younger riders wearing helmets and body protectors whipping the hell out of their horses or acting irresponsible because they feel as if they're immortal with their armour is ridiculous. It seems to give younger riders too much confidence for their own good. Take that protection away however and you'll see their confidence drain, because they know that all they have keeping them safe is the relationship and training of the horse.
On the other hand I am for the use of body protectors and helmets since they have saved countless lives as well as avoiding injury. It's reassuring for many that a fall wearing body protection will reduce the risk of physical damage.
However, there have been numerous cases where the use of body protection has in fact caused more damage to riders rather than protected them.
Personally I wear a helmet to ride, although there have been days where I have not worn one. It's more comfortable without, I will admit that, but safer to wear one. I used to wear a body protector when I was younger but stopped due to it bruising my arm when I fell. Additionally, I find that body protectors restrict your movement and can be quite unbalancing, but that's just me!
I like to say if you’re riding a horse under five, you should wear one just because they aren’t as reliable as they haven’t had as many exposures yet and will still have “baby brain”, so spooking/overreactions to spooky things happen more freaquently. In early stages of training they could also be more likely to become frustrated if they don’t understand something and possibly react with a buck.