What if the company will die if the problem isn't handled? Many companies (mine included) provide a service that needs to be highly available 24x7 (customers run automated tasks 24x7 against our service). If our site regularly went down for hours at night (or even for an entire weekend) because of a software problem that no one could fix because the developers weren't picking up the phone, we'd lose customers and eventually, the company would go out of business.
Even a 10 minute outage is a significant event and requires a full RCA for customers. We try hard to architect for high availability, but bugs do happen.