This is especially true for domestic travel as well.
As a US citizen, this is mostly just to validate any visa requirements for the country you're traveling to.
However, for non citizens, this data gets sent to CBP to create an exit record. I believe the concern is that between the check-in counter and the flight, you could trade places with someone to effectively overstay a visa without CBP's computer systems noticing (since you'd have a valid exit record)... hence the push for facial recognition at the gate.
At TSA, They scan the first page of passport (or local ID) and usually Full body scan. So in the strict sense of facially scanned no.
At the gate (until now), neither. They would scan the boarding pass and eyeball the passport if international.
Again the point here is that in the first two instances these are Government agencies doing the scanning. At the third, the Government no longer has anything to do with it.
The question with this stuff is how and where are Airlines (private companies) getting a database of biometric data and what are they doing with it?
Neither of which are good.