They can even be dynamic. Filter on location, uplink/computer speed, screen size, browser etc. None of it requires storing data.
Adtech might move to correlating all these things + the website visited to target particular demographics.
Adtech might move to correlating all these things + the website visited to target particular demographics.
ie: figure out why they are doing what they're doing and direct them to ads that capture that intent.
I think this much vaguer stuff will be fine.