The "gaucherie" points up the fact that Luca's loyalty was to Vito and Vito only. He couldn't relate to anyone else--not even to Connie on her wedding day. Luca would have been a rudderless ship without Vito. Other Dons might have approached him for his services after Vito's death, but Luca would have refuse. Sooner rather than later, one of the Dons would have had him assassinated--he was too dangerous to be at loose ends.