Actually the last part isn't true. The whole purpose of the metaplot during Matt Smith's first season was to effectively make it so no one knows about aliens. That's why Amy has no idea what a Dalek is during Victory of the Daleks.Empty planet + creatures that devour you to the bone? Silence in the Library.
Human race doomed by ecosystem meant to protect them? Gridlocked.
ETA
Crushing dystopia where everyone is made happy? Happiness Patrol.
Also Bill lives on Doctor Who's Earth where at this junction an alien attack wouldn't merit a "breaking news" strapline on BBC 24, so her questions sometimes grate.