The reason is simple. I once wrote a simple blog asking readers to compare two images, one of a beautiful mountain scene where I can easily see myself on vacation! The other image showed a hectic, bustling city scene with hundreds of bobbing heads walking along a crowded street. We often see the picture of nature as 'God's country'; the scene where we go to get away. While in this awesomely quiet woodland we will look at a calm lake, maybe see and hear waterfowl or hear the crickets, nothing else, and we think, 'this is creation'. Which scene is truly God's country? The only time Jesus left the hustle and bustle of Galilee was to be tempted, all alone in the wilderness; the rest of his life was spent among people, and a lot of them! Read through the gospels and see where Jesus ever got a break! Did Jesus ever really want a break? He was going about his Father's work, reconciling the world to God! When we see the word 'world' in scripture the reference is not to the earth, but the systems of society, of people.
What if Jesus was like me? I love to spend as much time as possible in the local wilderness. Jesus would not have accomplished much wandering through Yosemite! Especially not in 30 A.D. There is something for me to work on!
While there is definitely an advantage to visiting the countryside for a well deserved break, where can you most manifest the love that is God? I think the geese and possums already know who God is. The millions of people all around us may not. To me, the place where the people are is really God's country. Our purpose is to manifest God's love to one another and the best place for this to happen is where other people are.
This is why the images I used are of cities. Cities are full of people. People are a major part God's plan. If we lock ourselves away, we will miss out on many opportunities to show others who God is.