The physical aspects of life. The energy exchange require interaction with the environment. Living things require the presence of a universe if there is to be a large enough population of a certain organism. If you put a plant in a sealed bottle with water inside, it dies. Our lives require the exchange as well. No matter what it may be. When we close ourselves off from the world, we are missing out on an integral part of life. Experiences with the outside world shape our souls both positively and negatively, this leaves our hearts to choose which path we should take. How we react to positive and negative stimuli.
On the opposite end of the idea. We cannot solely take from our environment. We are a part of everyone else's experiences. Therefore thinking about our actions towards others or in light of others should be natural. No one want's to give bad experiences to fellow humans who are looking for the same thing. :] Give back.