A recent study indicated that Yarn and thread gives off certain Pheromones that actually hypnotize women and cause them to purchase unreasonable amounts.
When stored in large quantities in enclosed spaces, the Pheromones (in the yarn) cause memory loss and induce the nesting syndrome (similar to the one squirrels have before the onset of winter i.e. storing food), therefore perpetuating their species, and not having a population loss due to their kind being cut into pieces and mixed with others.
Sound tests have also revealed that these yarns emit a very high-pitched sound, heard only by a select few, a breed of women known as "knitters".
When played backwards on an LP, the sounds are heard as chants, "buy me, hook me, and wind me in a ball."
In order to overcome the so called "feeding frenzy effect" that these yarns cause, one must wear a face mask when entering a storage facility and use ear plugs to avoid being pulled into their grip.
(One must laugh, however, at the sight of customers in a yarn store, with WW2 army gas masks and headphones!). Studies have also indicated that aliens have inhabited the earth, helping to spread the effects that these yarns have on the human population. They are called "YARN STORE CLERKS".
It's also been experienced that these same Pheromones cause a pathological need to hide these yarn purchases when taken home (or at least blend them into the existing stash), and when asked by a significant other if the yarn is new, the reply is, "I've had it for awhile."