You can be any age and still get carded. If the store's compliance policy dictates that any sale of alcohol, tobacco, R-rated movie, Psudafed, etc, must be accompanied by a DL# or some other proof of birthdate, then the employee in charge of the transaction is responsible for either gathering that information or refusing the sale.
It's nothing personal.
The store needs to protect themselves and follow their own compliance policy. If a customer doesn't like having to give that information, then that customer can either not buy the product that invokes the policy at that store or purchase the product at another store.