Let me tell you a quick story about a common situation.
A Developer walks into the office and instantly notices that something isn’t right. His spider senses are going off. The room is electric, there’s a panicked look on a co-works’ face, as they types furiously. The two people in Customer Support look like they’ve been hit by a bus. He pulls out his phone, checking his email expecting the worse. It’s flooded with email. There was a software patch last night but the manual test team didn’t find any critical issues. “What is going on?”, they think.