Quoth Food Lady
We ID everyone, and yes, I do get people saying thank you. Thing is, does a 55-year-old really think I'm IDing her because I think she looks under 40? It should be obvious to her that I have to ID her, regardless of age.
The assumption is that while we do a quick glance, somehow we employees all have photographic memories and are therefore glancing at your address, your birthdate and your photo and can somehow steal your identity with just these bits of information.
Or that we'll track you down.