Sustaining Sustainability

So here's an important question that needs a good answer: why aren't more people buying into sustainability?  I'm not even going as far as to ask why don't they live sustainable, or engage more often in sustainable practices.  I'm just asking the most basic question: Why don't they buy it?

I ask this because a mere four months ago, even knowing a lot about it and having friends who were involved in it, I didn't buy it.  What sold me on it was the inefficiency of not living sustainable; thinking of the life that my daughter will live in the coming years; and finding a place to channel my effervescent energies.  

What are your reasons?