Nothing obvious is ever considered a "major decision" so the fact that the decisions are major points to plenty of pros and cons to them. So among those decisions where the prediction of the outcome is low confidence, it helps psychologically to take no personal responsibility for the decision making process and accept what comes as if it was what nature demanded. It makes sense from that perspective. But the main thing is the sorts of decisions one would leave up to a coin, in this study. They are by definition of ambiguous "happiness" value and the very fact of removing personal responsibility and potential regret from the equation, is enough to tip the "happiness" scale in favor of that decision making process.
It is for this reason that I believe in a system of government which would force all of its citizens, upon penalty of imprisonment, to make large life decisions based on a coin flip. It would be for their own good, and they would be happier. I care so much about other people that I would do that for them - force them to flip a coin to make their life decisions. Sometimes I marvel at how wonderful and pure my heart is, that I would go to these lengths, just to make other people happier.
