From the other videos some people seem to have gotten the impression that there are no cars nor children in Utrecht. But of course they are both there. It is just a matter of where you look and at what time.
This video was taken on a Wednesday afternoon, schools are closed on Wednesday afternoons in the Netherlands so plenty of children on their way. Also a lot of students riding around the city at that time. No people going to and coming from their work, but besides these commuters there are a lot of other groups of people using their bikes in the Netherlands too. As can be seen.
For a look in GoogleStreetView
Afternoon cycling in Utrecht