A web designer makes the shape of the car, decides what kind of tires it will have, 4 doors or 2, and most importantly the color.
A web application programmer builds the engine, connects all the wiring, puts the doors on the hinges, mounts the tires, and fills it up with gas.
A web application developer can work his tail off making the engine of the car move the car and to please the client the developer can add some piping that also lets the engine brew his coffee while he drives. The client might get excited about the feature but may never appreciate the effort that went into running the pipes for the coffee maker without adversely affecting the performance of the car or the appearance. While the developer de-prioritizes such minor things as the final washing and waxing of the car, the client fixates on "why hasn’t this car been washed yet?" and of course right after applying the wax the client will say "hmmm. Don’t you think this would look better in blue?" or "I think we should only have 2 doors."