Oh, I don't know, perhaps it's because it's not her job. Perhaps it's because it's her husband's job. He is the Prime Minister, after all. Or maybe it's Harriet Harman's job as Minister for Women and Equality, or Alan Johnson's job as the Home Secretary.
I'd have a lot more respect for Sarah Brown if she did campaign on behalf of brutalised women, but I don't think any less of her just because she doesn't. Catherine Bennett seems to subscribe to the view that every famous woman who doesn't campaign on women's rights is somehow a traitor to the cause, and wastes the first 15 column inches telling us so.
To her credit, she does eventually make valid points criticising Harriet Harman for something that is her job, but it's relegated almost to a footnote.
Can we please all establish that women's rights are really important and that it's a collective responsibility of Government, of the media, and of everyone else? Not just women. Not just famous women. And not just the Prime Minister's wife.
Come on Catherine, this sort of thing is your job, so why don't you use your column inches to inform us about women's rights? After all, you haven't written a really meaty piece about women's rights in your Observer column since, er... you wrote about Sarah Brown at the Labour Conference last year.
In the mean time you've been coating dead trees with your important thoughts on subjects such as the Princes, the Television Licence Fee, and the current lack of good old British political sex scandals. When you weren't attacking women politicians, of course.
Kettle: Hello Pot.Perhaps Catherine Bennett could spend more time writing on positive women's rights movements such as the Rights of Women, the Association for Women's Rights In Development, and the Muslim Women's Network UK. Organisations I'm sure anybody can get involved in, whether they're the Prime Minister's wife or not.
Pot: Hello Kettle. You're quite black, aren't you?
[Edit November 29th] In a fantastic twist, I just stumbled across this article in the Sun, from September, in which Sarah Brown speaks out on, er, women's rights.