Well, they've been producing HD content for over two decades now. Then there was Full HD (1080) that came out in the mid 2000s and already had a plethora of content. Initial 4K units came out roughly 6-7 years ago, becoming mainstream back in 2014. The problem right now is that very few major motion films are even recorded at 4-6K because the hardware to do so is limited and not mature like other camera systems. Sure, RED offers up to 8K, but the cost for rental on a production is higher than a 2-4K camera. Most films are recorded in 2K and converted up. Not a lot of films are being recorded in native 4K and up. HDR, well, that's just a color range.
http://realorfake4k.com/
https://referencehometheater.com/ultrahd-blu-ray-title-info/
I've been following this for years so it's not like I don't know the reasoning behind it. Just the majority of UHD material is actually upscaled video and not true 4K recordings exported as 4K. Planet Earth II is unique in that it's one of the largest documentary series (film if you want to call it) shot in native 4K and exported as such. Also had some scenes done in 5K and 6K. Very little scene work done in 2.8K.
Most TV providers won't ever support UHD as most who have the bandwidth capability send digital video that's capable at 1080i Mpeg 2 since 1080p isn't all that possible. On the other hand, satellite television providers do have the frequency ability to utilize 1080p video. Even FiOs (which is fiber) offers 1080i HD and not the p. 720p material tends to look awful on 4K, and that's what the majority of HD signal is today since investing in hardware to send out 1080i signal isn't cheap and thus it's limited in scope. Earlier 4K televisions were rather awful at correctly scaling the decrepit HD resolution, but now, newer televisions are pretty good at scaling 720p (HD) signals correctly.
It's infinitely easier for a provider to offer gig service (internet) and let consumers stream 720p, 1080p and 4K UHD+HDR material than invest in the hardware to make it possible via compression algorithms.
Generally, it's cheaper for ISPs to retain older bandwidth tech when it comes to digital video delivery and find better and more efficient compression algorithms than it is to invest money in an economy where more and more people are using online streaming. They open up more bandwidth to cable/fiber modems.
Future proofing is a good way to put it. However, some retailers offer and in-house upgrade component of additional warranties. You can upgrade in 5-6 years for a very small fee.
That said, we're looking at TVs at the moment, and I'm trying to figure out what the best is available now that also isn't buggy. Preferably, something with a decent remote, or upgrade everything and get one of those Logitech Harmony remotes.
The only real benefit in newer smart TVs is that they can now use 802.11ac and the 5 Ghz band, apart from better scaling.