It's probably just a personal thing. I'm in Europe and always take my birthday off - I don't understand why anybody would want to work on their birthday. Even if I don't have plans to celebrate until the weekend the idea of working on my birthday is very depressing (in fact in rarely celebrate my birthday and if I do it's something small like dinner with a couple of friends). To be honest I thought it would be more prevalent in Europe given we seem to get more time off and taking time off is less 'frowned upon' (at least this is my experience compared with my US based colleagues).
> I don't understand why anybody would want to work on their birthday.
I personally was under the impression that once you left childhood and the impatience of getting presents your birthday pretty much became just a day as usual. That also seems to be how my college treats it but it might be cultural. Europe is not a homogeneous place.