Earlier quoted context omitted.
There is also an incentive to display the proper status, since if you show all green when the service is down, you look dumb. We recently improved our status reporting because our old status system might not accurately indicate if only a part of our service went down, so it might show green even though (some) customers definitely saw very obvious downtime.
When the choice is between temporarily "looking dumb" and permanently loosing a bunch of money because of SLAs, companies like Salesforce usually make the latter choice.
In those cases status pages are more likely to have a lovely spectrum of yellows and oranges to choose from, but a distinct absence of red, but very few companies will say that they're fully green when they know there's issues. Green when you're down is usually more of a symptom of process problems in how outages get reported or resolved (no documentation, manual processes for updating, long communication chains from support teams to engineers).