Dispensary asking for passport

We went to a dispensary near our hostel three days in a row. On the third day, the woman at the desk asked us to give our name, date of birth and passport number. When we asked her why, she made it clear that she thinks it’s a dumb rule but she has been told to ask. She tried her best to explain but there was some stuff lost in translation. Something about returning customers, checking where we got the weed from, not really sure. Could anyone explain if this is common/the legal conduct? Been here nearly 2 months and first time it happened.

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