There is also a significant amount of personal risk tolerance involved. Casual riders can certainly have severe injuries, but easier trails are indeed easier.
I think it's way easier to get in over your head mountain biking than playing hockey.
A casual hockey player finding themselves in a way too kinetic game of pickup can nope-out pretty quickly, or likely won't ever get into the situation.
A casual mountain biker can go on a casual mountain bike ride with his brother and find himself way over his head, then bouncing down the trail on his head, very quickly and without an obvious offramp. Ask me how I know... ;)
I empathize because I literally just finished healing from an injury that came within millimeters of killing me because I followed someone into an area that I wasn't prepared for. The first hospital I went to, after doing X-rays said I needed a level one trauma center and called an ambulance to take me to Seattle harbor view.
I broke the cardinal rule of new technical terrain: pre-ride, re-ride, freeride. You get off your bike and walk the feature to see how approachable and rollable it might be. Then you session it (ride just that one feature). Then you ride through it quickly as part of a longer trail.
I went 5 years without an injury. This one healed in 3 months. I believe I know what I did wrong and can fairly easily avoid making that same mistake again. Do I expect zero injuries in the future? No.
What I expect is years at a time of an activity that very much enriches my life, with occasional injuries. Hopefully more than 5 years at a time since I'm making changes to avoid repeating the same mistake.
And I wish people knew that downhill mountain biking is a lot like downhill skiing. You can take the greens down or you can yeet yourself off something that's tougher than a double black diamond. I've gone on many group mountain bike rides with people in their 70s. So like skiing it is something you can shoot for doing into your old age.
