Let's imagine a scenario here:
On call engineer wakes up to an alert. Realizes there is a major problem developing that he or she is underqualified to handle. Escalates the call.
Eventually this gets escalated to the top subject matter expert in the company. He's not on call, has been out partying, and is drunk.
Where does this become unacceptable? I am certainly not saying people should show up to work drunk, but unless you say anyone in the escallation chain may never be drunk, it is going to happen.