That is a really stupid reason, because it doesn't make any sense. Why would the security agencies care how many concessions are sold? Why would airports provid

That is a really stupid reason, because it doesn't make any sense. Why would the security agencies care how many concessions are sold? Why would airports provide free drinking fountains with bottle-filling attachments if there was some governmental conspiracy to sell more water? The much more likely explanation is that there is some threat where the neer-do-wells would use X oz of something bad to mess up a plane or the passengers. Maybe X=5 and it is to prevent lone wolf attacks. Maybe X=21 and the argument is they would need to get 7 bad guys onto the plane to do it, which decreases the odds significantly that it could be pulled off without security agencies figuring out the plan.