We don't usually drink anything at the airport, but look forward to a G&T on the plane
I think if people are flying long haul and their destination has a big time difference from UK, then an early drink here, might be lunchtime/cocktail hour/nightcap wherever you are flying off to, and your body clock is going to be turned upside down anyway.
Or if you have got up at silly o'clock to get to the airport, then by the time you've checked in etc., you feel like it's lunchtime.
I know what people mean about needing a drink before flying, too.
I hate flying...but I just LOVE holidays, so it's worth it for those few scary moments of take off and landing