The facts that the book focuses on exactly the kind of patterns which are not abstractable into libraries in the popular OOP languages of the time (mostly true now, too), and that the implementation of each pattern is central to the presentation -- both of which arguably have quite good reasons based on the books intended role, to be sure -- I think promote this misunderstanding.

Certain other design patterns books in the software field (Patterns of Enterprise Application Architecture and Enterprise Integration Patterns, for examples that happen to be on the shelf next to me at the moment) don't share those features.