This is a very long-standing tradition. Before Dragon Magazine even existed, when TSR were publishing The Strategic Review, we had material from there get incorporated into the official rules.
Issue #1 of TSR had Gary's Random Dungeon rules... which were later published in the DMG.
The Illusionist, Ranger, Bard, Barbarians and many other elements of D&D first appeared in the pages of Dragon or TSR.
Cheers!
