Many scenes end up on the cutting room floor.

But, as the novel explains, it was only Luca who could make Vito feel nervous because Luca was an uncontrollable force. Luca let Vito control him. Also, Luca's reputation was well known in the underworld and allied community, so his presence might make some people uncomfortable. Afterall, it was a celebration.

"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
"Instagram is Twitter for people who can't read."