In Brooklyn, double parking may not be common during alternate side, but in Manhattan it is a necessity! Not enough parking spaces exist even with 2 sides of the street. Everyone knows that if you will need your car during alternate side make sure it is not on the “right” side of the street or it will be blocked in. It’s just a reality.
For the most part, cops don’t ticket people even though it is not legal. But I can remember when there was a job action and they just went up and down ticketing everyone. You can’t fight the ticket (unless it is defective) but hopefully 99% of the time you won’t get one.