On laptops 4k (and beyond) is wasted in one sense because you cannot run a 4k display at native resolution on a 13"/14"/15" laptop. Everything will be too small.
4k on a 14 inch laptop at native resolution can be useful for graphics work. I don't think that people are reading text at that resolution.
I run my 27 inch 4k monitors at native resolution and I can read text at that resolution but I have to zoom things in for anyone else when I want to show something on my screen.