Not familiar with NHK specifically (or, to be clear, I think I am but not with enough certainty), but it really makes a lot of sense for news networks to push for 8k or even 16k at this point.

Because it is a chicken and egg thing. Nobody is going to buy an 8k TV if all the things they watch are 1440p. But, similarly, there aren't going to be widespread 8k releases if everyone is watching on 1440p screens and so forth.

But what that ALSO means is that there is no reason to justify using 8k cameras if the best you can hope for is a premium 4k stream of a sporting event. And news outlets are fairly regularly the only source of video evidence of literally historic events.

From a much more banal perspective, it is why there is a gap in TV/film where you go from 1080p or even 4k re-releases to increasingly shady upscaling of 720 or even 480 content back to everything being natively 4k. Over simplifying, it is because we were using MUCH higher quality cameras than we really should have been for so long before switching to cheaper film and outright digital sensors because "there is no point". Obviously this ALSO is dependent on saving the high resolution originals but... yeah.