"Yeah, the family had a lotta buffiz,"
very amusing Mr Turnbull

The "living" that Vito gave Carlo was a dinky-ass storefront betting parlor. Even when Carlo said, at the dinner table, that he could be more helpful, Sonny shut him right down ("We don't discuss business at the table"--this after telling Clemenza to take care of the freelance Harlem numbers dealers),

Carlo knew nothing of value to Barzini. Even if he'd run To Barzini after Michael told him he'd be his "right hand man" in Nevada, Barzini wouldn't have taken him seriously. And anyway, Barzini probably was planning to kill Michael before he moved to Nevada.