Why do we create cities?

To start this post off, I am going to give my answer to last week's question: Why do people want to be seen as who they want to be? My answer is that people think that if they can look better, others will think that they do look better. That's rather mind bogglingly simple.
My family planned a hike today,  and I thought, why do we build these cities, and then crave for the outdoors we got rid of? Humans build cities, but some of us want to see what it looked like before the introduction of man, we want to see the natural landscape, to feel it. So why do we create cities in the first place? Why do we not live simple lives, like the native americans do? We build skyscrapers, space shuttles, and there are some of us who would want to live their entire lives in a forest.
That's a pretty short question, so this blog post will be pretty short. I also want to address an issue I have been having. Last night, I updated to OSX Yosemite (My family can't think of a proper way to pronounce that), and I found it annoying that they moved the fullscreen button on apps to the left side of the app window, when it used to be on the right. I want to know how to change this, because I find it annoying. Thank you for any feedback (or lack of, if you have no input)!