Get off the red paths and we're good. Jokes (?) aside, I don't think that's because of the cyclist profile but more about the people in the Netherlands in general. People are just not in a rush.
Cycling fast in the city centre is just too dangerous. The (big) city centres are small and crowded. Cycling really fast would result in grave accidents. Cycling for exercise is almost exclusively done outside the cities. Another reason to keep the pace down when commuting, is to minimize sweating.