You do realize that Rick Springfield grew up down under in Australia, I think, where there were no Schwinns.
The 1969 model introduction of the safety levers (a.k.a. "Turkey Levers") was massively popular and was what probably prompted the tidal wave towards racing handlebar bikes, because you could NOW RIDE THE TOPS and never have to go to the lower curved portion. Every manufacturer in the world copied Schwinn and began offering Turkey Levers on at least some of their lineup of 10 speed offerings. Most folks who bought 10 speeds during the BIKE BOOM specifically chose a ten speed model with racing bars and turkey levers. They also by an overwhelming majority, specifically wanted their ten speed to have their shifters located on the stem, rather than down low on the downtube. This irritates most younger "road-bike" enthusiasts today that despise stem shifters, turkey levers, steel wheels, one piece cranks, and any bike heavier than 28 pounds. They automatically associate stem shifters, turkey levers, steel wheels, and one piece cranks with undesireable, low rent bicycles that nobody should want to own and ride. As you can see, those youngsters haven't yet lived enough to know what a great riding old classic ten speed actually is.
The great, "COSMO's FACTORY" album (released 1970) , one of the best rock and roll albums of all-time, probably helped a little bit in furthering the popularity and coolness of the 10 speed as you cannot miss Doug Clifford's Schwinn on the cover.
That "COSMO's FACTORY" 8 track tape , sold in massive quantities, as did the L.P..
You would see that 10 speed each and every time that you would insert that 8 track into the 8 track player in your Volkswagen Beetle! Boon Boop Boop Boon bet you're wonderin how I knew.........