User blog comment:Tiredman2/Mass Effect Plot Holes and Contradictions/@comment-4953843-20120822075257/@comment-1679409-20120826182708

"it's also mentioned that turians have the ability to map huge swathes of space with groundbased telescopic arrays."

"Mapping," to me, would entail locating the physical locations of astronomical objects. In other words, "Hey, there's a black hole there; stay away. Hey, there are stars here; let's see what's around them.  Hey, this star has planets; maybe we should check them out someday." I don't think it is quite so easy to figure out if a planet (or a moon) is habitable just from mapping. Sure, you can probably figure out which ones are probably gas giants and eliminate those and see which ones are within a star's theoretical habitable zone, but that doesn't go far enough. You also have to study its atmosphere and see if it has the composition of gases, whether or not it has a magnetosphere to block radiation. And alien scientists have no doubt located scores of candidate worlds, but checking them probably takes time. Also, depending on which one Bekenstein is located relative to the Citadel (can't remember where), it may be blocked by the light of the galactic core.

I still agree that this is a puzzling question as to why humans got Bekenstein, but I don't think it's as easy as your imply for other races to have found it.