I believe they have tried fire-breaks, but the santa-anna winds can carry embers for miles. If you want perfect conditions for a fire, that is it. As the wind flows down from the east, it compresses and the moisture is wrung out. A nice strong dry wind, just what a fire needs to feed it.(along with trees)
We loath the fires, but it is natures way of recycling the land. From every devistating fire comes a new, more fertile forest. You can consider it the destruction of a forest, or the birth of a new one.