Too Much Green Screen and CGI!

I always wondered why passersby to a film/TV series crew shooting a scene in the street are so oblivious to what is happening.

I mean... many scenes take place on busy city streets or at sites teeming with tourists. 

Places which are practically impossible to close off even for a few hours in order to film a scene. 

And yet no one stops to stare at the big (or smaller) stars. 

No one is even a tiny bit curious as to how a scene is shot. 

Could all these people be so self-disciplined or just indifferent?

Could all these people (sometimes hundreds of them) be extras?

No. The answer is green screen (and CGI).  

As you can see from the following, very enlightening video which contains scenes from well-known TV series (I recognized Ugly Betty, Heroes, Grey's Anatomy, Monk, among them), street scenes are at best filmed on a closed off street, and at worst, completely inside a studio filled with green screens.

So much fakery.

The video is from 2009, so green screen and CGI technology must have advanced even further since then. However, it makes me happy that when I watch contemporary American TV series, I can at least still detect this artificial and confined feel in most of them.


Update:

I just found the 2012 video of the same visual effects company (Stargate Studios).
They are just getting better and better at this.