The Trough of No Value is the period in the lifetime of most objects between when they are new (and therefore valuable) and when they are old, rare, and collectable (and therefore valuable).
Who wanted to keep old lunchboxes around? They weren't useful any more. They weren't worth anything. And, since they were almost all used for their intended purpose, many were damaged or worn by use (I vaguely remember owning one that was rusty and had a dent). People naturally threw them away. The "trough of no value" for lunchboxes was long and harsh. That's why they're not so common today as you might guess -- because not that many made it through the trough.
My unsharpened NeXT pencil is still very much stuck in the trough, but I have endless patience. I hope to sell it for 75 cents someday. (thx, danny)