What makes people _think_ fewer FLOSS projects fail is that people only look at the successful ones because they are the most visible. Commercial failures are very visible because of the amount of money lost, people do post mortems, studies to "make sure we don't make the same costly mistakes again". With FLOSS no one cares about the failures, they just move on to something else.
IT is not alone in this problem, take construction / civil engineering, we judge by the failures: "this bridge has cracks, there are bits falling off this skyscraper, these houses are subsiding". We want impossible success rates: "why with all our building standards and fancy technology do we still get these problems". Then we look at, say, medieval cathedrals and say "see, those medieval stone masons had none of our fancy technology, they didn't have computers to calculate stress and strain, and yet they built all these beautiful cathedrals that have stood for centuries".
Why can't we be as successful as medieval stone masons / FLOSS projects ? Answer: you can. Just be sure to clear up the piles of fallen stone and above all do not document or dwell on your failures, move on and they will be forgotten.