According to Mabus, the breath tests are not intended as a crackdown measure but rather to help identify sailors who might be struggling with booze.
I was in a bar in downtown Singapore in the very early afternoon having a glass of lemonade. The bar was lined, bum to bum, with sailors off the New Jersey on R&R. They were all struggling with the booze. Their shore leave ended at 5pm and they were determined to get their monies worth.