It kind of feels to me that the market for HDR, is the same as that for 5.1 audio. In fact I often wonder when I'm sat watching something with 5.1, if I'm the only person.
Someone told me Sky are able to tell exactly how many people are using Dolby Atmos, because the Sky Q box flags it back to them. On one event it was just 18 people
I think the difference there is surround sound audio is a bit of a faff that people can't be bothered with, as it requires ideally an AV receiver with multiple speakers in the right places and you have to sit in the 'sweet spot' to get the most of the effect. HDR is just a new display technology like HD and UHD were and you can readily see the difference.
Yes, good point, though for an effective HDR picture you need a screen that can produce both a very bright image, and an inky black one. Most of the 'affordable' models can't, and you need to be spending a four figure amount, which does turn it into more of a niche market. That said, many will just turn up the brightness on their 500 quid screen, and go 'look, HDR', just as 20 years ago many took a 4:3 image and stretched it, saying, 'look, Widescreen'.
To be honest the benefit of 'inky black' pictures may be slightly overplayed in a domestic environment. Yes it's nice to have more detail in the darker areas of the pictures, but the real USP of HDR is that fewer highlights get clipped and instead carry on getting brighter, giving you detail where previously you'd just have a rolled off clip. Speculars and skies look so much better, even if you don't have perfect inky blacks at the low end. Yes - having darker blacks does make a difference - but I'm not sure that's specific to HDR as it benefits SDR too if you have a display capable of that. (Either using FALD LCD or OLED)
To be honest the 'inky black' thing is more an issue for OLED than FALD LCD as OLEDs don't go that bright, so to get the contrast range required for HDR they have to have better black level performance.
It's interesting that grading is now being done on high-end LCDs as much as OLEDs. (EIZO have a very good LCD display that outperforms the Sony X300 OLED AIUI)