Glowforge partnered with the Noun project to provide art for engraving - yes some of them can be cut, and people do cut them, but they’re designed for engraving. The outline feature in the GFUI allows you to add a cut line to any image so it’s a shortcut around something that might not otherwise be a good cut candidate
For example, this one the center should cut - but all those disconnected parts would just fall out!
Click on a design element and then click the outline tool (the icon on the right that looks like a mountain). Click create new outline. The interface generates an outline which you can adjust by sliding the blue dot left or right. You can see the outline change in real time.