4K may still be a niche among TV users, but that's because they rushed out the screens before the content, however these days for a lot of people who are gaming, watching blogs/music videos on YouTube and yes... ...using Netflix/Amazon... 4K is now a pretty much every day thing.
We may not need 8K yet, but the fact is if people want huge cinema screens in their homes one day or VR headsets that are as clear as real life, then the tech WILL be useful eventually and I would rather them do the work in getting it all standardised BEFORE I go out and spend hundreds or thousands on a new TV, you know like many early adopters did with 4K who are now probably a bit disappointed.
I can see why people think the industry should focus on getting 1080p and 4K everywhere before working on something higher, but honestly I think at this point it looks like we may see the industry skip over a lot of these resolutions until we actually settle for something long term, which I think 8K is more capable of withstanding.