You may be overestimating how many unique/different people travel through airports, especially more than once or twice to notice the tracking. People who travel once or twice total in their life by air, (are usually easy to spot), far more concerned with getting through a confusing hectic situation then noticing or even knowing that using facial recognition is new and not simply a special thing (because 9/11). And, the majority of Americans have travelled to zero or one country, last time I saw numbers on it. That country is usually Mexico or Canada where they drive (or walk).
I think once it starts trying to hit close to home where people have a routine and are not as stressed by a new situation and have the bandwidth to--at a minimum--take a pause, will ask questions about what is going on.