Most email discussion groups are not official support channels. There are a lot of peer-to-peer mailing lists inside Microsoft, consisting of people who are interested in a particular topic, sharing tips, providing advice, helping each other out if somebody runs into a problem, but they aren't the official support mechanism for the product group.
Here's an example based on actual events. Consider a hypothetical mailing list called Excel Users. Somebody asked a question seeking advice on how to set up a worksheet with specific characteristics and features. A second message was posted:
We are still waiting for your advice on how to accomplish this.
A peer-to-peer discussion group does not come with a service level agreement. These are just people who use Excel and help each other out in their spare time. There is nobody whose job it is to monitor the mailing list and ensure that every request for assistance gets driven to a resolution. If you want that, then go to the official support team.
What made this example particularly noteworthy was that the question was asked at 10pm and the demand for a follow-up was made at 10am the following day, barely 12 hours later, eight of which people most likely spent sleeping.