Most rooms don’t need acoustical treatment.

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. 

it all depends on your expectations for good sound. who is to say what you like, or what you will put up with.

lots of my top musical moments have zero to do with the fidelity, and everything to do with who i was with and what i was doing. top down, cruising the 101 in the early morning with my girlfriend on spring break in 71’, playing ’Here Comes The Sun’ on my 8 track is my top musical moment. who cared how it sounded? it was the moment.

OTOH if you do care about musical truth and fidelity then the room matters, and playing room roulette regarding getting lucky naturally does not work for many. symphony halls are not casually assembled for a reason. domestic rooms operate with the laws of physics also (slightly different than large halls for sure).

and at low volumes the room is not very relevant; but if you want to listen at live music volumes, then the room will really rear it's ugly head and make the experience horrible. you blame it on the recording, or the system, but it's mostly the room that cannot handle scale or dynamics.

here are some educational video’s if you actually want to learn about the subject.

https://www.gikacoustics.com/educational-videos/

if you have any doubt on this subject, go to any audio show and walk into 30 rooms and see if they all accidently sound good. if you love them all then find another hobby. this one is not relevant for you.

my friend doesn’t have acoustic treatments in his room

but then again, he is almost deaf

i hear quite well, i need 'em in my room for my system to sound really good

I have the Hifi in our living room and as you can see (from the following pic) room treatment wasn't really needed once the room was properly furnished with our favorite things.

https://media.distractify.com/brand-img/v6qRkZ-ac/2160x1131/sandra-hoarders-clutter-1559584060509.jp...

DeKay

Even for near listening most room need not only passive acoustic treatment but more active controls...I know that by experience and experiments... i know that because i read many times that near listening can spare me acoustic treatment and it is false in my room and physics dont change with room....But many people have not experience this fact because the listening in a moderately big room is not the same experience than in a smaller one....Then near listening in s small room is NOT AT ALL near listening in a way bigger room....

Acoustic is more complex than what we read in audio thread...

A  room is NOT a passive reflecting set of surfaces for the waves of sound to boucing off or be absorbed or being diffused... Like acoustical companies suggest to sell their materials... This is only half the story... A room can be activated and is a potential sets of different heterogeneous pressurized zones.... Helmholtz science...

Acoustic is more powerful than most upgrade...

No speakers at any price could shine in a bad room or even in an ordinary room....