Sustainability is about the how and not the why. It is a how to accomplish things with minimum adverse impact now or in the future, preserving resources for continuous use and supporting life using long-range life cycle thinking. Acting sustainably. The "why" is to make this world a better place to live in - a world where everyone has opportunities to thrive physically, intellectually and emotionally. A world of wonderful changes.
"Sustainable" sounds to me like a world of stasis; some perfect state of equilibrium where not much happens. A Utopia where everyone contemplates their navel and eats soybeans. BORING.
If you must use the term "sustainability," think of it as a path of evolution that will meander along forever. It's opposite is an unsustainable world where most populations crash off a cliff and there is little life on the planet left. I blogged before about thinking of "sustainably," the adverb.
My "Why" is to live in a world where there's a chance for everyone to thrive.
I say having a chance because success can't be guaranteed. We each have responsibilities to learn and grow and to not impede chances for others to thrive. There will always be lazy, irresponsible, mean, selfish, bad people. Plus, we will make mistakes. We don't know everything. We can't know everything. Good thing - as the pursuit of knowledge is necessary to thriving intellectually. We need to be thoughtful about the consequences to the complex systems we are part of if we do, or don't do, something. We need to act, but be ready to respond when things don't go as we planned. We need to strive for success, but keep the impacts of wrong choices as small as we can and learn from mistakes. We can't be "precautionary" in all things or we will fail to act and fail to learn and thrive. We have to try.
Nor can we delegate acting sustainably to somebody else - the corporate Chief Sustainability Officer or CSR group (nice article by Marc Gunther.), the green team, politicians, agencies, NGOs, etc. Each of us is part of the environmental, economic and social that make up our world. Our actions matter.
Why? We want ourselves and our progeny to thrive. How do we make that happen? By using "life cycle thinking" - acting "sustainably" - in everything we do.