I think there is a tendency, especially in our British culture, to give yourself the permission to let yourself go completely. He was probably surrounded by people doing exactly the same, which doesn't help.
We have the longest working hours in Europe, social isolation, a traditional inability to communicate with others unless shitfaced...loads of stressors (speaking in general here, I don't know Mr Toastie personally). And then it's considered socially acceptable, cool even, to get really, really drunk.
Bloody hell, I was on a small business course recently, and made a reference to saving half a bottle of wine for the next day, and the facilitator said "Oh, what would you want to do that for? I never have that problem- I always drink the whole bottle in one night"- and the whole group tittered in agreement 
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I speak as someone who regularly used to get too drunk right up until my mid 30s. It took 20 years and having DS to learn how to drink sensibly!