One of the basic premises of photography is aperture of lens you’re using to take a picture. The wider the aperture, the narrower the depth of field is and the more out of focus the background becomes. This is especially useful in portraits where all you want to do is focus on the subject and completely blur out the background. Nothing else matters, just the subject. The wider the aperture a lens can open up to, the more expensive the lens is, just because it is much more difficult to engineer a lens like that optically without introducing other problems.
Throughout my photography career, I rarely shrunk my aperture down. I always shot wide open or close to it. I paid for an expensive lens to make the background blurry, so why not do it? Turns out, there are many times where you would want a lot in focus. I recently got into an argument about this. I just cared about the person being nice and clear and the other person wanted both the person AND the background clear. It took me a while before a recognized the importance of what they meant. So I took it upon myself to run around and try to take pictures with the aperture stopped down to increase the depth of field.
The narrower depth of field tells the viewer what’s important – what exactly to look at. I find the wider depth of field to be a bit too busy. I won’t shoot with a narrower aperture in the future exclusively, but my mind is definitely a lot more open to it.