Well, there are a few points.
First, all new technologies are primarily used in luxury technology. Expensive TVs, huge panels, video walls, etc. These are all super-profits and prestige.
Secondly, these are patents and there is also a lot of money. Many companies, even very large ones, annually pay big money to the copyright holders of certain developments.
Third, these are great marketing advantages. "We were the first to invent ...", "For the first time in the world, we developed ...", etc. These are great informational reasons that bring huge image advantages.
In everyday life, of course, even 4K nowadays is too much. In an average apartment, where the distance to the screen is 3-5 meters, Full HD is quite enough. But progress (I do not know, unfortunately or fortunately) cannot be stopped. And all developers want to be first.
Well, for example, I use 4K at home. But not a TV screen, but a smartphone camera. Very comfortably. You shoot a video, then on the slowest rewind you find the most successful or funniest shots in high resolution, take a screenshot. Instead of spending a lot of time on a bunch of photos until you get one in which everyone is photogenic
More clarity to the god of clarity. On small monitors, I no longer see any point in further increasing the resolution, but on large screens it can be useful. Well, sell a new feature, as Xander said. At first there were HD-Ready, then Full-HD, then Quad-HD, recently 4K was loud, and now 8K. I will add Xandra a little, more resolution - more power is needed to work this resolution, therefore a new one is needed technique for such resolution. I just looked at the specifications of NVIDIA video cards, for 8K 10 series is required (https://www.geforce.com/hardware/desktop-gpus/geforce-gtx-980/specifications) Using the new resolution, you can re-release movies like re-released on FULL HD. Star Wars 8K edition, how do you like it? Of course this is a conspiracy-level theory, but very attractive.
Well, why? you need to sell it.
new formats are made not because people want to do it, but for the sake of money.
The buyer needs to be constantly stimulated, this is the law of the market.
must constantly feel that there is a better thing than he has now.
And if there is a fashion in clothes that constantly spins in a spiral, then in household appliances this is more difficult.
Here and you have to crush with megapixels, then 12 cameras, then a super large screen, then something else.