By my experience, this is probably the most popular and most active forum.
The reason you seem to think otherwise is probably because, as mentioned by previous poster, a lot of guys join this forum to get advice on one particular issue and when that probably doesn't work for them they leave thinking that forums aren't that helpful.
Also some members remain dormant for a period of time when they are busy or have other problems in their life. I just saw my 'joined date' and i was surprised to see that I've joined this forum for a year, while I've been mostly active since last month.