I find this fascinating as well. At this point, it's hard to fathom the reason they haven't announced that WDW is shut down through the shelter in place order at least. There is no way they can define themselves as an essential business activity so it's obvious they will not be open at least that long. I suspect much longer. I can think of a few minor reasons why there has been some delay, and we've come up with a few throughout the thread, but at some point you are just irritating your customers.
On the other hand, I'm not quite sure why people are waiting to cancel. If you are flying in from the Northeast you would have to wait 2 weeks anyway. And, especially during the shelter in place, there won't be any employees to run WDW anyway. So go ahead and cancel. I don't think Disney will give you anything extra, or penalize you any worse, if you hold out until the official cancellation.
** edited to add -- If you are after the shelter in place and driving in I can see why you'd still wait. But that's not in the 7 day window anyway.