I have an opinion:
IMAX goal is to reduce cost structure in order to add shareholder value. You see, they are in the hole about -25% year to date while the rest of the indexes are up about 20% during this Trump bump due in part of anticipated restructure of our tax system which is predicted to mainly benefit very large corporations and the very wealthy. In the mean time, middle class America is finding it difficult to afford such luxuries as theatre tickets for the common family of four, the gas to get there, parking expenses, and a round of lobby food, especially on a regular basis given budget restraints due to rising costs. Cuts must be made to satisfy balance sheets especially when you see the rest of the world whizzing by you. 3D and it's extra cost is the sacrificial lamb to bolster BOD and shareholder stakes at this point short term asap. (as if) More cuts and/or more perks may become necessary as middle class dollar value diminishes. Value incentives in a vying marketplace may be the next swoop for market share. I see some appearing now.
Attendance itself is nearing a 25 year low, not just 3D. Kids just don't date at the theatre with their sweetheart anymore. Most video consumption is done on a smart phone. Yes, many enjoy movie night(s) at home now just like staycations are also 'a thing'. These niches are numbered in the millions. Movie goers don't hate 3D. They are lucky they made it out at all given Moms budget they have to work with and a few extra bucks for each ticket for glasses and/or an IMAX showing might be just a bit over the top. They aren't haters like those running around the internet site to site, thread to thread, twisting knives and distorting facts for jollies or financial gain based on sites pushing this or that and shoving 3D out the way to make more room while inciting crowd mentality with raised fists . They are hard working exhausted folks looking for a distraction from reality they can enjoy. Many of us have been at it so long, it takes a bit more enhancement to blow our dresses up and 3D fills that want for many. I can't tell you the size of that little niche as you called it in other threads you envade, but judging from the even smaller niche of those that want to be involved in some small way by signing petitions and the likes just wish their voices to be heard. I'd bet there are 10 times that or more that do nothing, some lurking and others silently hoping it returns never reaching to the power of the internet to be heard at all. Streaming, HDR, Atmos, etc. are nice tech advancements but personally I don't consider them 'better' replacements for the 3D format therefor condoning it to the recycle bin to clear a wider path for the new push. When given the choice of formats for the same title I always go 3D. I've seen many titles offer up the UHD HDR version that is supposed to lure me into replacing the 3D or double dip it. I'm not going to double dip it because it isn't better, it's different and if I had both, I'd always reach for the 3D at viewing time anyway. I have the equipment to play 3D still. For UHD HDR titles only, my equipment covers that base well also. Thankfully, one major manufacturer is bringing 3D, 4k, and HDR back to the market in a couple months and I'd like to upgrade to a bigger display. I will probably buy (it) without ever considering the competition that chose to exclude 3D from their lineup at a reasonable cost ($2k). Their loss, not mine.