Generally speaking, because we can.
In Italy we have something like 2 million olive trees, and we produce 6 million quintals of olive oil each year, mostly extra virgin.
A wonder food
So we have an incredible amount of excellent olive oil — a wonder food that can prevent cardiovascular disease, has antioxidant properties, can help lower blood pressure, and provides excellent unsaturated fats. And it tastes great.
Not just oil
This is not to say that we don't use butter or other fats, especially in northern Italy. But olive oil is on another level.
The real question isn't how we eat so much olive oil. The real question is: how do you survive without it? Olive oil is the foundation of our longevity. Take it away and we'd become just like everyone else.


