I think it creates an illusion of barrier to entry. While an experienced cyclist can move faster and more efficiently when dressed and postured aerodynamically, there is really no *need* for such measures to enjoy a bicycle or use one to get around town.
I imagine quite a number of people could leisurely bike to work or around town but are put off by the idea of being hunched over uncomfortably in odd clothing.
Street protests, die-ins, etc helped the Netherlands get its bicycling infrastructure. In the 1960s and 70s, after the rising number of cars on Dutch streets resulted in over 400 child deaths by car per year, nationally, there were grass-roots protests that got the attention of the politicians. See this video:https://www.youtube.com/watch?v=XuBdf9jYj7o
This nice historical video about “How the Dutch got their cycle paths” concludes:
“To sum it up: What caused the changes in the Netherlands [resulting in so many bike paths]? There were the problems of cities that couldn’t cope with the increasing traffic that led to demolitions and to a public outrage over the amount of space handed over to motorized traffic. An intolerable number of traffic deaths that again led to mass public protests. An oil crisis and an economic crisis that led to gas shortages and high prices of energy. A solution was found in the political will on a national and municipal level with both decision makers and planners to deal with the situation. By turning away from car-centric policies and making way for alternative transport, like cycling. Cycling is now an integral part of transport policies.”