There's more to it than that... they get a thrill from the danger, otherwise these people's interest wouldn't all revolve around dangerous things.
Oh without a doubt the fear or the risk is a big part of it.
I wish I could find that "Science of Adrenalin" episode I spoke up thread.
They wired up the heads of different people and subjected them to various stimuli. They showed them videos of people walking tight ropes, jumping off cliffs, surfing, etc, etc.
The risk adverse people would almost be having a heart attack with any stimulus. Hearts racing, mind firing. The risk takers sat there as if dead. Almost bored the more of a risk taker they tested.
What they determined is that certain people who tend to be risk takers tend to walk thru normal life never feeling emotional highs and that can lead to some feeling bored, unfulfilled or even dead inside. They NEED to experience heightened risk to just FEEL like others feel.
They predicted this was a genetic trait that developed over millions of years of evolution with a small percentage of society as the most successful societies would be the ones who pushed the boundaries. Found new territory and took risks. But not everyone in a society can be a risk taker and in fact most cannot and should not. Most in society need to be risk adverse and stay home and nest and take care of family and all the stuff at home while others sail off into the unknown (often violent unknown) to try and find a better life for all.
It completely made sense.
They also said that serial entrepreneurs seem to be a way that a lot of these risk takers find an outlet without taking as much physical risk. They studied the brains of many entrepreneurs and found they have a similar response to stimuli and tend to require more risk or more stimulus to get a similar reaction.