White's advantage is an important thing to know because it affects how you play the opening. White can often "waste" a tempo in the opening for positional reasons but Black can easily be put in a bad way by the same kind of move.
In well-played games, White's opening goal is to maintain some overall advantage going into the middlegame and Black's goal is to achieve equality.
You can't go by W/L %, you have to look at predicted score based on elo difference.