I don't see problem here.
Not everybody interested in bitcoin already have bitcoin in their wallet.
If goal of this magazine is to have readers not just from bitcoin community but also from people not involved in bitcoin business yet, than it make sense to offer different payment options.
Yeah! A great reason, you're right! I also rather spend my USD, than spend my precious Bitcoins. I don't intend to spend them, otherwise I'd pretty soon won't be a BitcoinMillionaire anymore, hahaha!