In the days when I used to frequent RPG discussion forums on t'internet, I sometimes used to see people complaining about their woes of trying to run a 'sandbox' campaign. "All my players do is sit there!" a DM would moan. "We didn't know what we were supposed to do!" a player would whine. This seems to suggest a level of almost pathological passivity; given just the tiniest ounce of initiative and creativity, a rudimentary D&D sandbox campaign should almost be able to run itself from the results of some random generator results alone.
In my regular game, one of the PCs wears a pair of gauntlets of air elemental control that he inherited from a fallen comrade (he is actually the fifth PC to have possessed the gauntlets, the others all having died and passed them on to somebody new in their turn). They were obtained in a randomly-generated treasure hoard, and were identified shortly after, but they have never been used in anger - the party just hasn't happened to come across an air elemental at any stage since.
The player whose various PCs have worn the gauntlets at different times has always had it in the back of his mind that at some point he wants to use the damn things for their intended purpose. And at the last session he seemed to be hinting that at some point actively going out and finding an air elemental to command would be something he would like to do. This, of course, is the stuff dreams are made of: like putting the ball on the penalty spot for the DM to hit right through the laces. What greater spur to creativity does one need? All of a sudden, questions pop off in the mind like fireworks: where might there be an air elemental in the region? Who would know? What would it be doing, or guarding, or searching for? And why?
Random treasure hoards, in other words, just like random encounters, are a campaign-generation device par excellence. All that is needed is for the DM and players to be attuned to the notion that their results are not to be taken in isolation but as part of a cohesive world, and the game will drive itself along with only a finger needed on the steering wheel for guidance. All that one needs to do is to think of the campaign world as having an independent existence, and the things - everything - found within it as having an explanation waiting to be thought about and uncovered.