Having a police officer on a street is a crime deterrent, having 2 sat in the front of the van with God knows how many in the back is just a bloody waste of money. Those 3 officers could be deterring crime on 3 different streets not the 20 yards they're covering with their cameras sitting on their backsides.
Oh and being paid or not is no justification.
Oh dear. You are bitter and don't really know much. They aren't staffed by police officers. They are staffed by civilian staff. Also they don't have anybody in the back. That is for recording equipment etc.
Also I take it from you bitterness that this isn't a one off that it's parked outside your house which like Hans says, what are you/ your neighbours up to that causes them to constantly park there.