Along these lines, I was carded a few years years back...along with every other customer....at a large sports bar near a convention center. Given that I was approaching 50, I was more than a little surprised. I didn't exactly mind, but couldn't understand why they were carding people who were obviously "of age".

Later it was explained to me that the establishment had been caught serving alcohol to minors. Apparently a repeat violation. Long story short, the case wound up in court and the judge offered the management the option of being closed for a few weeks, or carding every patron (I believe also for a set period of time) as a condition of remaining open.