aren't a lot of bars in the US scanning the id card with some purpose-made id scanner? Seem to remember reading about that, and it being the US I would guess that data gets very much stored/shared/molested.
The scanner manufacturers proudly advertise that their systems dump the scanned IDs to a back-end database for storage and later use.
Yes, they are. The systems aren't even expensive, and they have some features like they track people who have been trespassed, etc.
However, you can buy fake IDs online, and the IDs are reportedly beating those machines. So if you trust the machine for age-verification, you might let in underage people.