[patmcc]

Two things - first, no typo, but in my jurisdiction legal alcohol age is 19, so +6 years is the margin of error (at that particular set of stores, anyway). Second, it's more about changing how the question is framed in the mind of the clerk. Instead of "is this person definitely over 19?" it's "is this person definitely over 25?" - which has a much safer error rate if there's a big penalty for selling liquor to minors and a small penalty for asking for ID when you don't need to.