You're right, I wish they would. I wish all of them would, but sadly the only company I've known to do so is Blu Cigs. Their video even says so. Others, well, they don't it is a consumable and the temptation for many people, especially cheap people, would be to claim a malfunction when there isn't one. I imagine that is the only reason none of them warrant their cartomizers. But, I wish they would because I've had my share of duds.
They could, at the very least, cover DOAs. I'm all for new ventures, products, etc., but over-embellished marketing is very dangerous for new vapors. I fell prey to a heavily overpriced ecig vendor in the beginning, but luckily got out without a whole lot of financial damage.