Bigger guys are more likely to show their stuff. I can’t even think of a “What do you think?” post with a guy that’s less than 7 inches.
I’m not sure about why it seems that they are posting more frequently. I think some have reached a comfort level and are now willing to post shots of their units. I also think if a massive study was done the average length and girth measurements would increase quite a bit. I don’t have any hard science to back that statement. Just my opinion.