I drink on my own quite frequently.
I travel a lot for work, and spend a lot of nights away in hotel rooms in random cities around Europe, so there's not much else to do other than sit in your room watching foreign telly, or go out and try to find a decent local bar. I've got favourite bars in places as far apart as Stockholm, London, Geneva, Madrid, Cork, and so on. And I'm almost always on my own when I drink there.
I also have rather a taste for real ale, so if I'm travelling around the UK, I'll often try to find a suitable pub serving proper beer and have a couple of beers (although I am starting to struggle in London, because I've found 3 or 4 excellent pubs very close together that all sell a decent range of real ales, and I rather like to work my way through them!). And I've also been to quite a few beer festivals on my own when I was younger....!
And when I'm "home alone" (such as when my family all bugger off to Spain for the whole summer), I get through a lot more beer than when they're at home!