GOOD question! I never get to tell this one either. Every time I start my family pulls the fire alarm. That is a sign you're getting old gang!
Back in the day (late sixties, early seventies in my case) it wasn't uncommon to find kits everywhere you went. The hardware store, five and dime, Woolworths and the originator of K-mart... KRESGE'S! They were at craft stores and the fabric store my mom shopped at began carrying them because of all the ladies hauling their bored sons through the store.
But in 1978, on a trip to Gramma's in West Virginia, we had to make a pit stop in Ripley. Dad wanted to get some oil for the car so I went into the Western Auto with him. In fact, a Western Auto store, so far was the one place I never saw model kits. I suspect auto shops, both body and mechanical, are the same way, with the exception of the "Promo" models that were pre built because.. why? You got real cars here. I have looked by the way, and have never seen them in a Western auto since, including that store.
There on a shelf in a corner were a few dozen models, priced at three dollars each. There was an Aurora Chitty Chitty Bang Bang in a tatty box.
I bought it and painted the red parts of the wings with my mom's nail polish. Then I assembled it with elmer's glue. THREE TIMES!!
This was during the days of sniffable adhesives and my Mom wasn't having them in her house.
i still have it, all taken apart and tucked away for one day...