A lot of shops run with minimal staff, because -- let's face it -- cost is a very large factor of competition in the hosting industry.
Then a problem occurs, and if it were an easy problem to solve, they'd just solve it straight off and then do damage control in PR. Or, the problem is more like this one, and it requires some hard and fast thinking on the part of the staff that are available.
If you're one of those staff, the last thing you want to do is distract yourself by logging in to a forum every twenty minutes, or checking email, or writing status updates every thirty minutes. You instead feel incredible pressure to get the problem fixed immediately, meaning you don't even stop for a bathroom break if you can help it.
As a sysadmin, you'll also justify your decisions by saying that telling the users what's going on won't really change anything; it's not like they're assisting you in troubleshooting. Even if they're intelligent, they still aren't familiar with the specific systems and network topology and other good stuff involved in your operations, so you'll probably spend a lot more time answering their suggestions than you would if you just got in and figured it out yourself.
Though as a user, that kind of attitude is extremely frustrating.