Well we all know that Ari was born to be a 몰, 두더지 in Hamas. Then if Hamas finds out that one of their agent's father is Mossad they would kill him and then Eli wouldn't have his mole...
I was wondering this myself; found the answer on the NCIS fandom page: "Ari Haswari was born in 1969 to Dr. Benjamin Weinstein (the undercover alias of Mossad agent and future Mossad director Eli David)".