re "Well, speaker recognition dates as far back as facial recognition does."
It was big in the 1980's to find interesting people using different phones and very early cell phones in South America by the US mil/gov.
The UK enjoyed using it "Spy-in-sky patrols over British cities in hunt for Taliban fighters" (3 August 2008)
"They are attempting to identify suspects using ‘voice prints’"
... "Traffic’ intercepted by the equipment on board is analysed and processed, probably at the GCHQ spy centre in Cheltenham, searching for voice matches"
The only real change is the cost of collection, cost of sorting and ability to build on public, telco, private and mil databases been shared with the Five Eye nations and friends.
Expect every arrival chatdown to be recored and indexed with your face, passport and the usual biometrics details.
Expect every car rental, duty free, cafe airport chatdown to be recored and indexed with your face, passport and the usual biometrics details.
Get you talking, keep you talking, its not just about the car rental use or been friendly to the wider travelling public
Domestically the telco and trusted brands Interactive voice response (IVR) will record the rest of the wider populations over years.
That 1 or 5 min chat with Bob or Sally in telco support is not just kept for training purposes or quality control
Your billing details have been matched with something globally unique.