Granted, the OP is showing an inappropriate level of hostility; but you bring up an interesting point:

Why should having women show up at a hackathon be a goal in its own right? It seems contrived, and doesn't do much to address the disparity of women in technology (in fact it seems to further enforce the notion that such contrived measures are the only way to effectively get women to participate in such an event.)

It has nothing to do with attracting women, unless you are suggesting that women can't program, and so the only way to attract them is to have fake hackathons like this? Don't project your sexism on me, I simply commented on the dilution of hacker terminology by marketing weasels.