... or you could give the money to Oxfam ...

How did donating to Oxfam come to be philosophers' moral cause of choice?

Whenever philosophers need an example of a good action that helps others, it seems, they speak of donating to Oxfam. How did this come to be? And, more importantly, does the frequent appearance of Oxfam in thought experiments help Oxfam's fundraising? I'd imagine that it's good publicity to be every philosopher's example of a good action.

Oxfam's message seems to be getting through to the philosophical community, at least, as there are many philosophers who donate to Oxfam or encourage donations to Oxfam. But is there any evidence that the thought-experiment-based publicity has caused an overall increase in their donations?