I have known a couple of people who have joined HubPages without Google AdSense accounts ask this question.
I think Google have changed policies to make sure that you write consistently before you become elligable for an AdSense account.
I hope this helps. You are not alone in having that requirement placed upon you.
On the bright side you can write a lot of hubs in 6 months and when you become elligable you'll have a good portfolio to provide residual income. Happy Hubbing.