Wildland managers have, over the last 100+ years, made a huge mistake in the management of their forest acreage. They put out all of the fires. Most fires pre government management (see Joe's remark above) would burn the undergrowth and small timber ("dog hair") but the mature trees are left standing in most fire situations when fire regularly passes through removing the understory fuel. Local tribes in western states are often attributed with traditions of burning out the chaparral every few seasons. When you let that fuel build up by continually putting it out after lightning strikes, it's like building a bonfire under the standing timber, and then you see the mature growth crown out when the ground fire is so hot convection ignites the tops of the trees.

The discussion over the last 20 years has been how to clear out that undergrowth without setting off huge fires that destroy the standing timber. Mechanically crawling over all of that acreage is physically impossible if even if it were, would be beyond any budget to practically manage.

There are fire retardant foams that can be sprayed on structures to help prevent total destruction. http://www.latimes.com/business/realestate/la-re-fire25nov25-story.html