Parking in Park Slope

What's the deal with the doubleparked cars in Park Slope? If you notice in this shot there are actually two rows of cars stretching the entire block- those parked legally by the curb and a second row doubleparked waiting for the alternate side of the street parking regulation times to expire so they can move to the open spots on the right hand side of the street. This is all pretty clear.
What doesn't make sense to me is that all these cars are empty. I'm not sure if this is a Brooklyn thing or what, but from what I've seen in Manhattan, car owners will sit in their car while waiting for the spots to become legal- and they will not doublepark but on a block like this they would all be on the right hand side of the street already claiming their spots. If the street sweeper comes, they move to the other side. If a cop comes, they turn the engine on and the cop moves on. But there would never be an entire block's worth of cars waiting; only a few.

So what's the deal here? Where are the car owners? Do they all just live on this block and are keeping on eye on their vehicles from their windows? Did about 20 car owners hire one guy to move all their cars from one side to the other twice a week? Isn't this an open invitation for a traffic cop to come along and write out about 35 tickets in a row? What happens if one of the legally parked cars on the left needs to get out? Are they just waiting for the street sweeper to come by before moving over to the right? Why is it so different than Manhattan? Can anyone explain?