For example, if I put a Scarf Jirachi on my team, and I get first pick at IVs to lower, I might make it so that my Scarf Jirachi can revenge anything on the opponents team, and will not have to risk a speed tie with even the opposing Scarfer. Building on this, if I lowered said Jirachi's Speed IV on my opponents team, and I have a DD Salamence, there is no way he can revenge it while I can revenge his Salamence with my perfect Speed 31 IV Scarfed Jirachi. Just something to think about I guess.