It's more "this is our contractual obligation, if we're down more than this, then we might not charge you"
They are typically limited to the amount that you actually paid, though, so basically they don't charge you for the time when you couldn't use the product. You usually won't get more than that.
This outage alone has spurred conversations in slack about how terrible JIRA is and why we should replace it. If this kind of shit was pulled, I can guarantee we'd be on shortcut, linear, or something else in short order.
Atlassian absolutely can in enterprise settings. In my company (a large cloud company), if JIRA goes down, large swathes of the business will also stall, including code deployment (deployments are tracked through change management JIRA tickets). We also use the DC version of Atlassian products, so presumably we aren't be at the mercy of Atlassian cloud engineers.