Olives are too bitter and toxic to be eaten right off the tree. Almost every olive sold in the market is cured (either fermented in Brine or chemically boiled with Lye)
It can take as long as a year (depending on the temperature & style) to cure the olive and make it into a succulent garnish that you would put in your martini and other finger foods.
Urban mankind is getting cut-off off from the food production & processing. For us our every meal comes in cartons or wrappers and we don't realize that there is fermented food all over... Bread, Cheese, Curd, black tea, idli/dhokala, chocolate, coffee are something that are ubiquitous but we still don't realize that they are fermented food.