One likely reason they’re still on X is so those that didn’t get the memo to use their app or otherwise can’t still can still get alerts. Switching to multiple accounts would require people who likely wouldn’t notice to follow the others, and those that would do that would hopefully have downloaded the app. And yes, if a person isn’t noticing they need to get the app they likely won’t notice a critical alert, but when you’re dealing with people’s lives everything counts.