Interesting and until recently I felt the same, but 4K TVs are becoming more prevalent and though broadcast is only 720 (HD) satellite and cable are making the jump soon. So it's about being future proof. But already with faster streaming 4K is available for web viewing.
Though I love the cinema films are now watched more often on a small screen.

Another important thing is shooting 6k on a red dragon for example, allows you to over frame a shot and then crop in. Meaning a well devised mid wide can give you alternatives on many other frames. Only one other angle set up may then be required (again allowing multiple framed reverse or side shots) speeding up a shoot alternatively you can frame wide and digitally track a subject as a cropped mid or close up. Thus having an expensive camera requiring a more expensive edit suite (hardware) could save money on a big shoot, in time and grip equipment.
For most hobbyists and budget pros it is probably still an unnecessary luxury, if you do go for it I'd say only do so if you can also afford full frame. I've argued in the past that with higher resolution is full frame such a biggie, but recent experience would say it is. You just get that look.