Why do some people feel the urge to take on mentally and physically demanding challenges and often scarily dangerous feats? Sailing solo around the world - climbing Mt Everest - walking across Australia - freefalling from an aeroplane are just a few.
My daughters have come to the conclusion that it's basically a "bloke thing". It fulfils some primordial urge to escape from the comforts of home (and probably the wife and kids!), to be free of responsibilities for a brief time and to be free to explore "new horizons". Testing self survival skills to overcome problems along the way is an essential element of the challenge.
Del's motto, when facing a challenge, is "Don't think about it , do it!" - and you can be sure that he will!