Yes we did this in the past, but we changed it last year, because it was causing troubles. To ensure the best quality we always want to have the "release" binaries in beta channel first for few days to see if it's stable, before we push it for general use.
Yes of course we have our internal QA, automated/manual testing, but we are never able to simulate all scenarios, machine configurations etc that exist in the real world. Here is the great help of the beta community.
I hope this makes sense..