Most rooms don’t need acoustical treatment.

I have never needed acoustical room treatments over 50yrs of audio. All rooms had furnature,  drapes, to dissipate sound reflections to acceptable levels. What has helped incredibly is all DIY speakers I have built have infinately variable control over the mid and tweet so room adjustment is simple for room brightness. 

As someone always looking to optimize the sound of their system, I had been reading about the virtues of acoustic treatments and the mention of GIK acoustics several times on the 'gon.

A fellow member friend got some treatments from them that were acceptable to his fiancee and he said it improved the sound some. He said he wanted to do more, but wasn't allowed.

I followed suit and spoke with a very nice, honest guy from GIK, sent him pictures of my room and he told me what it would take to optimize the acoustics of the room given the large open, multi purpose, multi listening positions, unique layout with all the openings. I am not having problems, just always looking to improve when it is worth it.

Net net, I was willing to get a few things and he told me that unless I wanted to get a much more significant number of bass traps that would heavily change the look of the room (and my marital status) it wasn't worth it for me to make the couple additions I was planning on.

I appreciated his refreshing honesty, and if you have the commitment, I would recommend using them. I think any room can benefit from them. Whether the improvement is worth it is up to you. They are a proven science, but I think more appropriate for a recording studio, theater, concert hall or dedicated listening room. And especially for stereo stores or special setups at audio trade shows. That's what their web site focuses on. They are pros.

Not snake oil, but many people buy stuff that they may not need, blind and expect miracles.

The only way to really assess a listening room is to have someone with the gear and software they need come and test the room, preferably with all the furniture in it that you want already.

I lucked out - I had an arched false ceiling already, which solved some of the issues I might have had, and a live wall (glass doors) that we solved with some heavy acoustic curtains.

I could easily have spent many times as much on supposed 'improvements' if I hadn't actually had the room tested

My advice is to pay the money for testing and see whether you have any issues - many can be addressed relatively cheaply.  There is probably a home theatre business near you that can do it, (though they'd rarely be called out for pure audio).

I agree with the OP.
You do not need any room treatments. At least not while you’re using your headphones.