This was tested and they found that this made the water quality worse, because the Dutch tap water is already of high quality and the water filter makes it dirt

This was tested and they found that this made the water quality worse, because the Dutch tap water is already of high quality and the water filter makes it dirtier because bacteria start to grow on it after a while. In fact, the water company filters the water through the same type of activated carbon filter, except that the filter in the Brita is at best a couple of centimeters long whereas the filter of the water company is 2x250 centimeters long (and they use other filtration steps, not just activated carbon).