So Raul would you say a high percentage of the trees don't set fruit? If you were to guess, what percent would you say do fruit?
As Oscar and Raul noted, wild trees are going to behave differently than trees in cultivation. You must realize that most wild trees are not growing in full sun and are not being cared for by humans as commercial/back yard plantings. It's not like a human grabs the wild fruits and disperse them naturally in perfect spots and then babies them. Wild trees are subject to the conditions where they sprout and grow and those conditions are variable. I observed them in their natural habitat during fruit development season and saw many of them growing in full shade - and though they had signs of previous flowerings, those trees were not carrying any fruit. Some wild trees get "lucky" and end up in better growing conditions than that (sunlight) earlier in their lives or right away and will have a different more full growth (compared with trees growing in deep shade) and likely produce more because of it. But those would still be different from commercial/yard plantings. This is true with most if not all wild fruit trees compared to commercial/yard plantings.