To use the example Mhairi Black gave. If you're down in Westminster, and you're scheduled to vote at 11pm. But you've done all your work by around 7pm.
The temptation is to go and kill time with a pint, rather than sit around in the office twiddling your thumbs. And one pint so very easily can become a second pint, and then spiral to too many pints.
It's especially more tempting when your drinks are heavily subsided.
