Some think, including many Dutch themselves, that bike paths have always been there.... Cycle paths weren't really necessary [when] cyclists outnumbered auto traffic by far. After WWII, everything changed.
Specifically, Dutch incomes went up dramatically in the post-war boom, more people bought cars, and many more lane-miles for cars were built. As auto traffic grew, the risk for cyclists--especially children--increased noticeably. During the oil crisis of the early 1970's, the government instituted "car-free Sundays," which showed people that they could still get around cities without their cars.
In 1975, the government created "demonstration routes" in The Hague and Tilburg to encourage cycling. The video says that "in retrospect, this was the start of the modern cycling movement" in the Netherlands.
Why do bike paths qualify as micro-institutions? First and most simply, they are coordination devices. According to the Pedestrian and Bicycle Information Center, "Bicycle lanes make the movements of both motorists and bicyclists more predictable and as with other bicycle facilities there are advantages to all road users in striping them on the roadway."
Second, in this case they were clearly a result of government policy to encourage a specific behavior. Third, protestors played an interesting role: see the video at about 6 minutes in for an example of an "informal" bike path that protestors created by painting the pavement. Later on, it was formalized into a modern bike path.
None of this is to suggest, as some would, that the greatest need of the US today is more bike lanes. Rather, it is to show how quickly an informal micro-institution can become formalized, and then how soon people think of it as something that has "always been there."