I think the canon reason given for this and other "why didn't the ship's computer just stop them?" situations that it's a privacy violation to just go around scanning people without their permission.
Although they do seem to do a lot of "scanning for life-signs" so who knows?
I remember reading those Dev journals too, but I feel like they helped me to get more out of B&W than most other people.
Yes, it was all about building hype, but it meant that I played more in a "find-your-own-fun-and-set-your-own-goals" way, which I think was what the original intent was.
Everyone's biggest complaint was that the missions were half-baked and felt like they were thrown in right at the end. And they were right.
It's based on the same technology that makes you turn faster in Mario Kart if you tilt your head and turn the controller like a steering wheel.