This statistic says that about 10% of Skarmories in the high ladder hold salac berries. It was collected from people who were good at OU, so I'm pretty sure they knew what they were doing. I personally can't think of any good reason to desire a speed increase. It's not like Skarmory can sweep or anything.
After Sturdy activates it lets Skarmory lay down one more layer of hazards when up against a faster Pokemon. It's the next best option since Custap berry isn't released yet.