Do you need to strop after sharpening?

No, but it makes life so much easier if you do. Using a strop adds a few positive things to your sharpening process. The first is you can see it as an extra fine addition to your grit progression. Extra fine stones tend to be relatively expensive, but a strop and honing compound can be relatively inexpensive. The other positive is that since strops are usually made of a compressible material, it makes it a lot easier to remove any burr that you’ve created during sharpening. A burr is a thin wire edge that forms during sharpening. If you leave it on then cut something, the burr can get torn off, leaving behind a relatively blunt edge. You can deburr on stones, and it’s a skill I recommend you practice, but using a strop to deburr is just easier. To properly deburr on a strop, make sure you’re stropping at the same angle you were sharpening at, use very light pressure and when you reach the end of a stroke, flip the knife over spine down. If you flip the knife edge down you risk rolling the edge against the strop, blunting your knife.