Except no one is expecting to not be outsped by Weavile, meaning they will switch and hope for the best, Its a slight risk but considering that the entire set is based on your opponents assumptions being wrong, why not take it farther?
Also, Why settle for forcing Azelf/Gengar to switch when you can just deal away with them completely?
[SET COMMENTS]
<p>With the advent of the Focus Sash suicide lead that focuses on nothing but laying down Stealth Rock and preventing the opponent from doing the same, Weavile stands out as one of the few Pokemon that can combat this trend.