I dunno. I have read pupa (up tp most recent chapter as of this posting, actually), and I have read elfin lied.
They are similar in a very general sense, but (and correct me if I am wrong) I don't recall the element of eating other living things/victims in elfin lied - esp not with the watery, slurpy, lip smacking graphic sounds the pv showed. -_-
For us who have not reviewed the finished product (like we assume the tv channels, etc. have) all we really have to go on is the preview as a litmus test for what the ful version of anime could be combined with the manga chapters themselves. And in that light I can kinda imagine why it has not been permitted to air thus far.
And tho it is just my own opinion I don't think that marketability is the lone consideration. Even if it is, that doesn't necessarily mean that the reasons it is assumed it would not be matketable are necessarily bad ones.
Just my take on things though.
