911 is a creaky old system put in place by a Chicago mayor looking to score some points with the electorate. There are thousands of (poorly run, uncoordinated) Public Safety Answering Points across the country, and most tend to contract with just the local incumbent telecom, ensuring any time there is an issue with said incumbent, every call to said PSAP fails.

In the context of most of these PSAPs having already moved to VOIP, there isn't a coherent reason why these calls shouldn't go straight from the carrier originating the call to the PSAP, without middlemen like Centurylink standing by to misroute those calls.