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ELI5: How are knives and other sharp objects dulled by weak, soft materials like paper, etc

We have scissors and knives and my wife is always telling me not to cut paper with the "good" scissors because they'll dull faster, literally making me feel like a 5 year-old.

Disclaimer: she's not treating me like I'm five, I just feel that way because I've heard it since I was a kid.
gpt
Take a stainless steel knife, and take a slab of meat. Which one is sharper and stronger? The knife right? The meat is not hard enough to scratch the knife. 

Now hold the knife in a vice and beat the crap out of it with the slab of meat. The knife bent in half, but how can that be if the meat is softer than the knife? 

That's basically what's going on as the edge on a knife gets duller (excluding things like minerals, sand, dirt, grit, bones, etc wearing the edge down) is that an edge is not perfectly straight or smooth. It's made of many microscopic daggers of metal like fine little teeth that grow from the edge.

As you cut things, these little metal teeth will start to bend to the left and right even though they are harder than the material they are cutting. When this happens you end up with the edge having microscopic mis-allignments of the teeth on the edge. 

This is easily corrected by steeling the blade. You've seen chefs do this by scraping the blade up and down a metal rod which takes the bent teeth of the edge and stands them back up straight. This doesn't really sharpen the edge by removing material, but by straightening the material already there. Once this is done the knife is sharp again. 

Barbers may also do this by stropping a blade with leather before using it. The leather takes the place of the steel and re-aligns the teeth on the edge of the blade. They may also use a stropping compound which is a fine abrasive which also removes a small amount of blade material and polishes the edge, making a more comfortable shave. 

After a lot of use, or rough use, the edge itself may lose it's shape and at that point it needs to be re-honed or sharpened. The less material removed to get the blade sharp again, the longer the blade will last. 

Here's a knife pro tip. You can strop any metal blade using nothing but cardboard. Cardboard is a very rough kind of paper and it is very high in mineral content like silicates, glass, etc which are harder than the steel in the knife. If you cut a piece of cardboard and lay it on a table top you can take a dulled knife and scrape it backwards so the edge is dragged back across the cardboard. Do this several dozen times, always pulling back against the edge, not pushing forwards against it, and make sure to do it with a light touch and alternate the sides of the blade every few strokes. Do this and you can put a razor edge on almost any knife you own.