Crikey, you'd have to have large swathes of stores under lock and key, increasing the cost for everyone. Great idea, especially when most stores can successfully make necessary checks for those people who look under age, noting that it is not a requirement to prove your age if you are & look old enough. A sledgehammer to crack a nut solution methinks!I suggest there is a flaw in how shops operate. Customers should not have direct access to items (e.g. alcohol) where an age-checking policy operates - they should have to request shop staff the get the item after providing proof of age evidence.
(Of course most supermarkets would object to such a policy as it might reduce sales of alcohol)