How come not a soul tried to install fire sprinklers and fire hydrants on their vertebrae yard? These equipments could have save houses where raging fires are possible. ...

These equipments could have save houses where raging fires are possible. Developers should be required to install these equipments or at least backyard fire hydrants where on earth necessary.
Answers:    You must be from the city. In the suburbs and within the country, there is not necessarily hose pressure from rural water lines to suitably service a hydrant, or water well are used. Hydrants cost over $2000 or so, and do need a strong plenty water pressure to function. As a former firefighter surrounded by a rural area, I can detail you we were prohibited from hooking up to the hydrants surrounded by most of our service area, they be on 4 inch lines and had deficient pressure to serve a fire engine. My fire engine could pump 1200 gallons per minute, but the hydrants could provide only just about 200. A hookup to an inadequate hydrant can in actual fact cause the entire hydrant and part of the pack of the water row to be physically pulled out of the ground, I saw it happen once. Not pretty. My fire dept relied on tanker trucks to shuttle sea to our fire scenes, big city guys rely on hydrants, so they don't know what to do surrounded by suburban areas where here is no water. We be always call in to "assist" contained by the neighboring city in areas not even so served by city water as the city have no water tankers.
I saw Michael Reagan on Fox the other daylight griping that the environmentalists are to blame becuase they don't allow the govt. to "manage" the forest and clear brush. Heck, the entire area is primarily brush, smoothly. WHat is not managed is the process of allowing folks to move out into semi-arid regions like the hill and mountains around southern California. Sure it is pretty, but how much is it costing for these people to live within their potential fire pits? Prevention is the key in attendance. Also people don't build to protect their investment, they want it pretty--wood shingles, wooden deck, lots of wood to catch fire. Note surrounded by many of the pics, the stucco homes beside tile roofs are still standing in plentiful places, and homes with cleared areas around them, properly "managed" to protect their homes.
Easy answer....Costs. Everything is outstandingly expensive in California. That would one and only add to the already inflated costs of homes.