Because your particular outage might be on server related to or involved in a "system wide" outage that gets fixed, while your problems is on a lower level that is not resolved by the "system wide" problem being abated.
DH would "clear" the "system wide" status, but your problem would remain, and they would have no way of knowing that your problem wasn't resolved. I believe the message stating the "system wide" is resolved also cautions you that ,"if your problem persists, submit a support ticket", or some words to that general effect.
I suggest submitting a support ticket forthwith! (it appears the "system wide" issue was not the source of your problem, and you need to let DH know to get cracking on it )