T0: Servers go down T5-15: Someone realizes something is broken. T15-45: Initial someone calls another someone to tell them it's broken because the night guy probably can't fix it all by himself. T60-70: All the engineers are woken up and know OF the problem. T90: Engineers figure out WHAT the problem is. T120: Engineers fix problems. T150: More problems arise. T180: All problems are solved, no more customers are mad.
Moral of the Story: As you can see, it already is a very involved process to get servers running again. Now, as a customer, you want an email to notify you that services are down. First, the admin needs to find out exactly which customers are affected and then write up a nice happy email to you letting you know we're working on it. Do you want a happy email or do you want your servers fixed? Your call. Downtime is chaos. Do not ask to be notified of chaos.
It's not like the two are mutually exclusive. Are you really suggesting that the entire 180 minutes of effort by multiple engineers would have to be directed at writing a "happy email" rather than fixing the problem?
The real reason, I imagine, is that if they automatically sent out an email to everyone who could be affected then more people would know of the problem. It's probably smart to accept a handful of customers being unhappy about being in the dark in return for the outage being exposed to far fewer customers.
And they could have a script that directly posts to the status page something like "A lot of our servers are down, we are working on it please be patient" when they detect some problem wouldn't take long...