Because he’s not going to continue to have a 0.79 WHIP without more strikeouts. The BABIP gods giveth and the BABIP gods taketh away.
https://www.fangraphs.com/leaders.aspx?pos=all&stats=pit&lg=all&qual=y&type=8&season=2023&month=0&season1=2023&ind=0&team=0&rost=0&age=0&filter=&players=0&startdate=2023-01-01&enddate=2023-12-31&sort=12,a