I think it is often more about simple incremental improvements in picture quality than the 4k format. See how it compares to your old TV while running it as 1080p!
You may sit close enough and your screen may be big enough such that you can see the 4k difference, but last time I looked at a chart of distance vs resolution vs screen size, 4k seemed like a pointless option.
But then, I only have a 70" screen!