Might be the strength of beer also. 4/5 pints of American beer finishing 12 hours before flying and you’re good to go at 0 the next morning. 4/5 pints of some of the nicer Ales/Lagers particularly the craft stuff around Glasgow, not so much.
I remember previous company had similar issues in Belgium. No one did anything untoward/illegal but after a few boisterous room parties a gentle reminder that most of the beer is 8/9% not 4/5% made a few suddenly think.