Nexus phones ARE dev phones. The original Nexus One was pitched mainly as a dev phone:
They remained as largely dev phones until the Galaxy Nexus when Google realised there was potential for a stock flagship. Then came the Nexus 7 and 4 which have evolved to be aimed at consumers just as much as they are developers. They are vanilla enough and cheap enough for developers to easily use as test devices, and at the same time they have become more appealing to a wider audience with Google's endorsement.
Before the Galaxy Nexus, Nexus phones were largely for developers, hence why they had relatively low sales, but since the Galaxy Nexus, Google have shifted the focus towards consumers now. It's important to note, that when the Nexus One launched, Android was still far behind Apple in marketshare terms, so promoting the Nexus brand to developers was a smart way to get them on board with Android as a platform, just like BB are doing with their Dev phone series. But now that Android has overtaken iOS in marketshare, they no longer need to convince developers, so they have shifted their focus to consumers, hence the heavy advertising for these new Nexus devices. It's quite a clever strategy really and it seems to have worked.