As a rule, WI does not have assault as a crime. You might find it in some specialized areas (restraining orders, e.g.), but not in the regular statutes. Attempted battery, maybe.
But why is an intentional killing considered more culpable? This is clearly a moral judgment.
Note also that many of the extra kinds of offenses (e.g., homicide by intoxicated use of motor vehicles) could easily be classed in one of the main categories. They get their own special treatment for a variety of reasons.