Why doesn't Hamlet kill his uncle immediately after his father's visitation?

"Hamlet is a momma's boy. His concern throughout the play is not primarily on avenging his father's murder, but on chastising his beloved mother. From the beginning, Hamlet is more upset about his mother's hasty remarriage than about his father's death. In his first monologue (I . 2 : 129-159), wherein he reveals the cause of his despondency, Hamlet speaks almost exclusively of his mother's crime, famously noting, "frailty, thy name is woman." And when, in response to his father's charge, Hamlet turns his attention to thoughts of revenge, he first exclaims, "O most pernicious woman" before thinking of his uncle (I . 5 : 105). It is his mother's crime that weighs most heavily on his heart."