Why would they? Code from 1987 is of exactly zero interest to someone developing a game in 2013.
I suppose just examining the original media might have been enough. Or maybe they abandoned that command style? I didn't play the remake.
In 1991, they remade the original Leisure Suit Larry to be a traditional point-and-click adventure game. It's referred to as Leisure Suit Larry 1: In the Land of the Lounge Lizards or just Leisure Suit Larry 1 VGA. The modern-day remake was an update of the point-and-click version.