Agree with the above. It's just a matter of luck and persistence, mostly. Clearly, most DMGs were actually used in gaming sessions ... and, as we all know, all of the
1e hardbacks tended to break down pretty quickly with use (especially the front covers).
However, some were stored, and there's no reason these books shouldn't be nice and crisp. In fact, when you find a nice copy, it will make an unmistakable
crack sound when it's opened for the first time.
Nice
1e hardbacks are out there ... but you'll need some patience.