Somehow I don't think simply "seeing" an airplane or two every now and then, or even on a daily basis, is going to make a difference when it comes to getting minute (but important) details correct on a model, such as the right engines or the correct wing to fuselage root.
These factory workers are obviously not aviation enthusiasts if they have never seen a plane, so seeing one off in the distance isn't going to help one bit. They won't even know what kind of plane they are looking at...
I'm no car expert, so driving around, casually observing traffic isn't going to help me build a model of one. Even if I was looking at a certain characteristic of a certain type of car, I would still need good, detailed, photo references.
Having an "idea or concept" about a plane isn't what the workers need. They've got the concept down, it's attention to detail that they lack.
And also, cars are a lot less complicated that planes.