Extinguisher training is important as most folks think you shoot at the fuel that's burning rather than the gas escaping that is actually what is on fire. Because of this, a lot of extinguishing agent is wasted by most regular folks and makes extinguisher use ineffective many times. Extinguisher training was actually much better when we had folks putting actual fires out in a pan full of flammable liquids. But environmental rules have pretty much eliminated that in today's world. Now it is video simulated, so there is no way to know if the student is actually applying the extinguishing agent at the right location. Getting close enough, proper aim, etc... are all important, and it is much better to have done it once under training conditions than to try to do it for the first time when it's hot, actually on fire, and there are plenty of folks doing chicken dances around you.
As far as sprinklers versus deluge systems, 2 different types of fires and 2 different types of automatic response. Can't be compared to what we are attempting to do in the desert at races. Those systems are engineered specifically for the occupancy and types of materials that will be burning. At a pit, crap shoot if the number and type of extinguishers are enough to put out what is burning. And that does not include the human factor trying to put the fire out. And extinguishers should be out, on teh ground, at the pit ready for use, not just when your car comes in, but also available for when the pit next to you decides you don't know what you're talking about when you tell them not to fuel out of that drum in the bed of their pick-up truck that is sitting on a plastic bed liner and not grounded. Fortunately they listened after their truck was on fire.