Whether we synthesize an AN for generation or decoding purposes, we would want the synthetic AN to look as much as possible like a real AN in its natural usage contexts, and cooccurrence vectors of observed ANs are a summary of their usage in actual linguistic contexts.
it might be the case that the specific resources we used for our vector construction procedure are not appropriate, so that the specific observed AN vectors we extract are not reliable (e.g., they are so sparse in the original space as to be uninformative, or they are strictly tied to the domains of the input corpora).