When we read text on a monitor, lots of tricks are needed to make it look acceptable given that the number of pixels involved are so few: anti aliasing, font hinting to remove display artifactsm and so on. These are only partially effective, and you can usually see the pixels in some way. For vectors it's even worse...no font hinting, sub pixel alignments are common, plenty of crappy artifacts. Compare to reading from a high ppi laser printer...everything looks so nice and smooth. Today, our displays are still dot matrix.

Basically, a 5K monitor gives you the experience of not being able to see the pixels...what you see looks more like a high quality printout and less like pixel art.