Those teams being stall teams.
I haven't played on the ladder for about a week (Not on the leaderboard anymore either =( ) but I'm pretty sure placing Scarf Primape on a Stall team is a bad Idea. Primeape can't take anything but resisted Hits, or Sleep.
I'm sure a particular type of stall could employ it, but why not just use a Bulky Sleep Talker, it fits better with a stall team.
And Scarf Primape actually makes a decent lead. Not only for Darkrai, but it can outrun Deo-A Leads, get them down to 1% then switch to something to absorb whatever they throw at you... which is much easier to predict considering Primape is fairly Light and Superpower is a bad move to fire of Randomly, especially when all you've scouted is the lead (which granted is probably scarfed)
And for anyone who says an UU that has a niche in Ubers sucks, you're clearly not using whatever it is properly...














