downhill runs reach beyond 50 mph
at that point one mistake is death
provided your bike is tuned to withstand the set up a natural frequency, you still have to fight nerves and break pads
you need remarkable balls to successfully navigate a downhill mountain leg
period
The downside of extreme risk-taking is that you may not survive it. Many don’t completely grasp that.
I did an 11 mile downhill run on Mt Ranier when I was young and stupid. Pushed off from Paradise Inn and didn’t turn the crank once all the way to Longmkre, WA. No helmet. A French “Bertin” bike that was no great shakes. Couple of motorcyclists came up beside me and one of them taps his speedometer and says “You’re doing 45.” The folly of youth. On the return climb, I remember somebody poking their head out of a van and snapping my pic. You didn’t see many mountain bicyclists in those days.
You also need questionable judgment to do it...or a death wish.