Any time I've been in an age-restricted venue here in Australia they have taken a picture of me and my ID at the door.

Even so, they likely aren't recording everything your eyes see and for how long they linger. They likely aren't recording your entire traversal through the venue, what you do, what you say, what times you go there, from where you connect, etc. Simply being at a public place is one data point. A full history of your entire interaction is a magnitude different.