Most rooms don’t need acoustical treatment.

Mofojo is right.  We do know how a car works.  On the other hand, we don't know why someone prefers a blue one to a red one, or a Camry to a Prius or why anyone  likes the Fiat 500.  (Well, maybe in some cases we do--like why I prefer my 88 Volvo wagon to anything built in the last twenty years that would cost me 30 or 40x as much).

You wouldn’t happen to have a blue 88 Volvo Wagon and live in West Mi would you? 

Room treatment can be tricky. Unless one can  determine what and where specific (!) problems are occurring and apply treatments to treat those specific problems at those specific locations, one might make things worse.

False. Panels can help greatly, even in cluttered rooms.

The "knowing how a car works" is still a valid analogy.  While many have a general understanding of how engines, brakes and steering work, very few of us are mechanical engineers and have a detailed understanding of the design details and why certain choices were made. And keep in mind that even engineers tend to work in very specialized areas -- you don't hand the development of the car's suspension to the engine team.   

The same is true with many of the technical devices we use daily. One does not need to be an electric engineer or app programmer to use our cell phones or laptops.  

The same is true of acoustics and room treatment. It is a discipline that is well understood by the specialists in that area. However, what is obvious to them may be much less so to the rest of us.  But that is the beauty of audio as a hobby -- it is easy to experiment.  If you get good results, great! If you make things worse, they can generally be easily undone.  And no one is is danger or has their life ruined by the process.