My guess is because we currently don't use our email lists for developer conversation. That all happens on IRC and here in the forums. There are build notifications (failures and fixes) published to the dev list and JIRAs to the issues list, but I believe those are screened from the search results.
p.s. I promise to start posting more short videos on SwitchYard HOW-TOs. Just need to get 0.3 buttoned up first.