While what you say seem intuitive, it is missing one point. Those locations probably are not recording exactly who is coming and going and what they are saying/doing.
That is where this become more than just gate keeping and becomes full on tracking.
You are saying something quite different to the comment I responded to:
> The right people to protect children are those responsible for them - their parents and guardians.
My position is that there is a social responsibility to protect children which extends to the community at large, not just their immediate guardians.
A lot of clubs in a lot of places scan and store your ID on entrance.
When venues (bars, clubs, supermarkets) scan your ID, they are scanning the barcode on the back.
For details of what is stored on that barcode:
https://www.aamva.org/getmedia/99ac7057-0f4d-4461-b0a2-3a553...
What's on passports and some identity docs:
https://en.wikipedia.org/wiki/Machine-readable_passport
There have been many cases where clubs stored the documents scanned which were then hacked. Or where club/bar staff used the scanned/stored documents to stalk attractive women.
Sample:
https://www.theverge.com/tech/947157/passports-data-breach-c...