Why do crown ether look the way they do?
Crown ethers don't look like that except in structure drawings

You confuse two completely different things: the drawings we use to describe chemical structures and what molecules actually look like in real chemical environments. We draw crown ethers like this because the drawing accurately describes the connectivity in the structure. In reality crown ethers are flexible and floppy and certainly not flat. we don't add that extra complexity to 2D structure drawing as they get very messy very quickly and obscure the essential features that describe the connectivity in a simple way.

When they are in solution with appropriate ions (for 18-crown-6, potassium ions would be a good example) they form complexes driven by the attraction between the oxygens and the charged ions. These complexes have 3-dimensional structures (with K+ the complex is approximately octahedral as potassium fits neatly into the cavity created by the oxygens when the molecule folds up). It looks a little like this as a 3D structure:



Wikipedia has some good descriptions of this and further pictures.

Crown ethers are not rigid molecules and the actual shapes they take up in 3D space demand a lot on what else is in solution with them. Other, similar, complexing agents are far more rigid. Calixarenes, for example, have a 3D shape like a chalice which is even more misrepresented by a 2D drawing.