I don't know if any of those 'regret' it. I know I as a fan I carry a bit of a grudge. I think we fans were deprived from seeing the best of the best. And, I think that each has their own heart about it in retrospect. A few of those around the world, not just those mentioned, more than likely are simply mercenary about their golf and it is an ATM machine work-a-day job, while others may feel national pride sentiments and pangs of regret.
As far as the risk calculations, Zika, crime, whatever... every other athlete there runs the same risk. Life is a risk, but maybe these pro athletes from all the glory sports just aren't hungry enough for the thrill of the competition and the absence of another big payday is a manner of risk factor for some of them. Thus, I am still nostalgic for real amateur athletes in the Olys.