Allusions are far from being the sole preserve of literature.
Cinema, painting and music frequently contain quotations from other works. Early still-lifes in particular depended on a rich vocabulary of symbols which many admirers are unaware of today. This, however, increases the risk of the allusion being missed and if the intrinsic meaning is plausible but weak, the reader may miss much. Plagiarists hope that the marker won't be recognised at all. There is no longer a canon of work that the reader can be expected to know - readership is wider, the Bible is less popular, and there are more books.