When Dungeons & Dragons was published, it included a full range of monsters and treasures. This gave referees both sufficient things that could be used out-of-the-box and lots of of inspiration.
But they also became—to an extent—canonical. We tend to assume that the bulk of these things exist in every DM’s milieu and that the bulk of them are as described in the book.
As new editions were published, each sought to round out those lists even further. And the canon grew. While there is always room for our own creations, adding them to the already crowded lists...
Imagine what it was like for players in Dave’s Blackmoor campaign or Gary’s Greyhawk campaign, to encounter these things for the first time not in books, but in game.
Perhaps we should strive to use nigh none of this stuff exactly as published in our own campaigns.
Is this at odds with my “let D&D be D&D” principle? I thought so, but I’m re-thinking that.