I have to say, the lack of a default setting in D&D does honestly kind of annoy me. Having gon through the player's guide and DM's Guide, it bothers me that the game tries to have it both ways, not giving a default setting and working on the assumption that you're going to create your own, yet still talking about everything as though there were a default setting. Most games I've interacted with have a defined setting, and the ones I've seen that are actually setting agnostic don't make the kinds of player-character assumptions D&D seems to. There's clearly an assumed setting at play, but the books dance around telling you what it is and leave all the hard work of actually world-building to the DM. And yet it still makes assumptions that, if a DM doesn't want in their setting, they then have to do the work of adjusting out.
