I often wonder the same thing, my guess is that some people may meet beyond the SketchCrawl gathering and get home late. I suspect a great number may continue to enjoy the weekend (specially Sunny days), and not get a chance to scan their results until much later.
For the last few events I typically wait for a few hours and if nobody posts a result (for San Francisco), I will create the topic (in case someone else is not sure about creating it and/or is afraid of being first
- since I am local to the area) - Once someone posts, I remove my initial inquiry post.
I moved your post over here, because you inquiry is actually applicable to many location. I think in general everybody (including you and I) are so eager to see what people sketched that we just don't want to wait