According to Professor Jonathan Touboul, a mathematical neuroscientist at the Collège de France in Paris, there is always a delay between the time a trend begins to gain traction, and the time hipsters begin following it.

This delay is caused because people can’t be aware of what others are deciding, in real-time.

As a result, hipsters gradually realise that the trend, and the decision has been made while making the same decision separately. 

This leads to them gradually conforming towards what then becomes the mainstream.