To be fair, there was previously no systematic exit control process in US airports unlike in many countries including the Schengen area bloc, and many other countries have also long required photographs of non-citizens/non-residents along with exit controls. The US is more in line with the UK, Canada, etc. approach that doesn't allow any way of way of definitively knowing whether someone on a visa or restricted permit actually left the country if they were supposed to.
While I would have preferred a non-biometric approach for everyone, I'm hoping that moving some of the burden to exit control 1. lessens the workload of immigration enforcement domestically, and 2. encourages a very slow transition towards more seamless international transfers given that US airports usually weren't built for this, although a lot more work would be needed here.
My understanding is the that airline passenger lists are the equivalent exit “check” for the US and Canada. They are shared freely between the two countries as are entry checks into respective countries (hence the US or Canada can confirm an exit based on entry to the neighboring country).
That said, I think it’s mostly just “we can check if needed” and it’s not matched up automatically though that might have changed? I know if you’re an immigrant and you check your I-94 record with USCIS is usually wrong and missing data.
To be fair, the concept of passports (in the modern sense of a document required to cross a national border) is a relatively modern invention, on the close order of only about a hundred years.
While I would have preferred a non-biometric approach for everyone, I'm hoping that moving some of the burden to exit control 1. lessens the workload of immigration enforcement domestically, and 2. encourages a very slow transition towards more seamless international transfers given that US airports usually weren't built for this, although a lot more work would be needed here.