Well, not all. But in many good photos, the background is blurred. Because one way – a very good way – to draw attention to your subject is to blur the background. You do this by using aperture or manual modes and selecting a large aperture (a small “f-number”, like 2.8 or 2.0 or even 1.4 if your lens can do this).
That is why I love the 35mm f/1.4 lens and several f/2.8 lenses I use also: because they allow me to dramatically blur backgrounds. Like in a few of last night’s guests:
The other interesting thing is that these pictures make you guess; make you piece together the story, as in my post the other day.
Tip: Normally, you do not want the blurred background person to vie for attention by looking into the camera. Except if they are the only person, as in this image:
Your eye goes first to the cake. Then to the gentleman in the background. Then you try to make out what is happening.
And sometimes selective focus is all about drawing attention to the eyes:
The good news: there are many affordable fast lenses available, like the 50mm f/1.8 that many camera makers sell, and the 35mm f/1.8 that some sell.
If you are not yet shooting with fast lenses, probably prime lenses, my advice is to try it soon.