Maybe because 4K is what gets me interested in video, perhaps?
How do you like your 4K TV? Also, what computer/UHD-monitor/software setup do you have to edit your 4K video?
Why all the attention to output, not to the process?
Are you using your digital images always without cropping, printing always at maximum size?
There are benefits for having extra.
Just to back up of having 4K capability for producing 1080p output:
4K 8bit 4:2:0 on the Panasonic GH4 converts to 1080p 10bit 4:4:4