In my opinion the jump from 1080p to 4K is as significant as the jump from hdd to ssd. That's a lot of screen real estate and especially when programming I put it to use.
Examples:
https://github.com/Tecate/bitmap-fonts
If you're on 4K you can simulate how they look on 1080p with 2x integer nearest neighbor scaling.
The by current standards normal sharpness is nice too (1080 screens aren't really blurry, they're pixely).
I basically went back to 1080p because of this.
Eye resolution is ridiculously high. There's a reason companies started marketing 'retina' displays.
Small fonts will not always fall into discrete pixels which is especially true if the resolution is not very high. Which requires you to do antialiasing or mangle the characters.
Higher resolution displays allows you to render them more faithfully.