I think you're looking at it the wrong way - triggering the flight or fight response won't make you able to fight or flight by itself. You have to practice the responses or they're useless - detrimental even, like a deer in the headlights

Play is a way to exercise those instincts and practice responses, but in a safe way. We even creep into the danger zone a bit sometimes, but most people (and animals) keep the danger measured

Fear isn't pain - it's not meant to be an absolute deterrent. It makes us think twice and go into fight or flight mode to handle a challenge - it doesn't discourage behaviors, it moderates them. Sometimes you do have to face off a rival, or need to take a risk for a reward. It releases endorphins if we come out of it better off

So it's not weird that we are drawn to it - horror stories/movies/games trigger it artificially, but so does fighting each other or tests of courage