Miloh,
Actually, the FAA does need to inspect the final product. The kit planes are listed as "experimental" planes and you do need a pilot license to fly one. I worked for Mark Brown in San Antonio, Tx. laying up composite parts for a kit plane called the Pulsar. The kit, to be qualified as a kit, has to have at least 51% of the assembly done by the builder and not the company offering the kit. We would offer either a full-blown kit, much like Top Flite does, or we also had a "ARF" version that came with the wings built and several other items already made. It was up to the customer. At the high point of our sales, we were selling 5 kits a month and it was all that we could do to keep up with the sales. We also offered orientation flights to potential customers. Sort of like a check ride to get you up to speed on how to fly it. You were expected to be a fully licensed pilot by the time you were done building it and were ready to fly. The FAA expects you to keep a log book of the building progress and then they inspect it before the first flight.
The only kit plane I'm aware of that don't require inspection, or even a pilot's license are the "ultralight" classification. I guess they figure that you are taking your chances on that thing folding up like a cheap card table, so you're on your own!

Here's a shot of the Pulsar we made with Mark Brown, designer, at the controls:

Jesse