[wiml]

A library book is a relatively expensive object (not necessarily the physical book, but the whole cost of having the book at the library). Spending a couple dollars on a durable tag that is permanently attached to the book makes sense.

Retail stores had to wait until people developed much cheaper tags, because each tag only gets used once. These cost a few cents per tag, and are different from the 13.56MHz tags that the library probably uses.

[hiddencost]

I can buy rfid tags for 10c in bulk on Amazon.

[wiml]

Hm, you're right, even the 13.56 tags have come way down in price. Anyway, I think my point still stands: RFID as a technology used to be more expensive, and used to be at a price point were tracking an asset like a book or a shipping crate through multiple uses made sense but tracking a bottle of milk through a single purchase didn't.