Hence, I build in points of tension and potential conflict as well as Other Actors with Agendas that will be able to either support or oppose various things the PCs might wish to do.
My perspective is similar. The worlds to be built with a high degree of potential for PCs to get involved, whether that's working their way into the criminal underworld of the city, or poaching aurumvorax for their golden pelts. But I try not to design things for the PCs. I try, and am not always successful, to decide where the dragon's lair is based on where it *should be* not where it is level appropriate (just as an example).