[aeternum]

It could be that Google Maps is saving everyone time by doing this. The Braess Paradox is really interesting, and this could be an attempt to prevent it: http://vcp.med.harvard.edu/braess-paradox.html

[Ericson2314]

I would imagine introducing cars to a road itself causes a braess paradox.

[aeternum]

Introducing cars does cause more traffic.

However the interesting thing about braess paradox is that even if you keep the number of cars constant, introducing a new road can make travel times worse.