When Schwinn Dealers were selling Schwinn's faster than they could assemble them there was no longer a good reason to change the name plate.
In the 1950's Schwinn began to promote its brand name nationally. Captain Kangaroo on TV, Schwinn ad's on the back of every comic book, and Boy's Life were national ad campaigns. Schwinn Bicycle Company (Arnold, Schwinn and Company) offered a co-op (cooperative advertising) program to its Schwinn Dealers where the dealer could send in his "approved radio/TV/newspaper ad's" into Schwinn (attention of Ray Caparos) for a 50% reimbursement. The dealer could advertise Schwinn and his store like a hero in his own small town, and Schwinn picked up 50% of his advertising bill. There were some rules to control this program. The approved ads had to have all of the requirements of the FTC truth in advertising rules. You could not advertise the photo of a Paramount and show the price of a Pixie for example. The advertising had to be on the up and up. You could not show any other bike, or any other brand in a Schwinn Co-op'ed ad and still get the reimbursement. Schwinn approved many different kinds of Schwinn Dealer local advertising, like fence signs at the dealers local Little League, BMX track, or school newspaper. I even knew of highway billboards for Schwinn Dealers on the co-op program. The dealer's advertising budget was based on the number of bikes they purchased annually. Co-op advertising simply stretched the dealers available advertising dollars to go further, they did not pay 100% of what he advertised.
With the Schwinn brand driving more buyers into Schwinn dealerships during the 1950's there was less reason for a dealer to sell and promote his "house brand", or his "local distributor's brands" even if they might have been "Built by Schwinn".
I would credit this change in marketing direction to Ray Burch.
John