I've never seen one buy a round of drinks...

Are men more generous than women?
Is somebody keeping score or something?
Obviously it matters to the huge and growing "philanthropy" industry. If they can figure out the differences they can craft those alumni fundraising spam more cleverly.

In this thoughtful article about giving and gender, researchers touched on some examples which made sense to me. Their conclusion was helpful as well:

While there is nothing wrong with encouraging males to be more empathetic and females bolder in their charitable donations, ambitious programs for resocializing children to be more like the opposite sex are ill advised and, in any case, of unproven effect. The truth – not likely to make headlines in London or San Francisco – is that both sexes have their graces and their own styles of being virtuous. Determining which sex is the more generous is like deciding which is more physically attractive: there is no objective answer. Henry Higgins and Charles Darwin take note: when it comes to generosity, the sexes are different but fundamentally equal.