Most people want to believe racing had more to do with developing the modern bicycle than any other activity.
Gears weren't allowed in TdF before 1955, but gears were already prominent for decades in bikes for transportation.
BTW, roads were first paved for bicycles - not for recreation, but for transportation.
Only in the US did Henry Ford change development of the bike to kids toys - in the rest of the world, bikes were developed for transportation.
I believe the biggest single step was made by the French constructeurs, especially during the WWII occupation.
Bikes for utility, bikes for hauling - there was a daily pedal race to get produce from outlying farms to Paris markets.
650b was the original gravel bike.
There was no gas, no automobiles, France was not at war - everyone had jobs, and their transportation budgets went into nice bicycles.
Jan Heine's great article
When I was researching our René Herse book, the most difficult part of the story were the war-time years. Herse started making bikes in 1940, while Paris was occupied by the Germans. Being conditioned by war movies and war-time memories from German relatives, I found…
www.renehersecycles.com
Modern marketing has very little to do with the history and development of the bicycle - it's simply where most cyclists get their information.