What's the point of "draining" yogurt?
Often, yogurt will drain away excess liquid in that length of time, thickening the yogurt. If left to drain overnight, a lot of yogurts will drain away a huge quantity of whey (yogurt water), some yogurts will hardly release any. If your yogurt didn't release whey, that just means that it was good and thick to begin with. That's great, but don't assume that your next container of yogurt will be the same way, even if you get the same brand. If you drain yogurt and it releases whey it will be a lot thicker than it was before you drained it, making the resulting marinade thicker in the bargain.

In the US, that's the major difference between Greek yogurt and "regular" yogurt like Yoplait original. Greek yogurt is thicker because it has been strained. "Real" Greek yogurt may also use different cultures, I don't know, but in this country the difference between Greek and "regular" is straining. 

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