I disagree, there are a lot more gigs that get mentioned in the Gig and Event Announcements forum, and indeed on the rest of the site, than are advertised in the GCG. I think it's more a question of promoters not realising that they have to add the event to the calendar itself rather than posting an announcement in the forum. In the past, the mods would add events to the calendar that were posted in the forum, but now the promoter can bypass the forum and add their event directly.
I've had people complaining that we're not doing our job properly in the past with regards to the calendar, so I refer them to
this.
It's a free service that gets thousands of hits every day, so I don't see why promoters shouldn't take advantage of it.