We are getting undercut by those wanting to live the same life as us. What these people don't understand is that they are lowering said life style.
Who's going to stand up and say so, when everyone is so focused on climbing higher in the world themselves to escape the "not as good as it used to be" level they're at now?
A person who wants a lifestyle of "more", for example everyone ever to exist, doesn't really know what that lifestyle of "more" is actually like, so they have no frame of reference to know if they are damaging it. They just know that it's "more" and therefore must be better than what they have now.
In their eyes it doesn't matter how much of that cliff crumbles on the way up, because they are still higher up in the world when they get to its summit. Who cares if it's a foot shorter and everyone standing on it is now a foot lower and angry with you, as long as you can see over the heads of your former peers, right? But wait, there's always another plateau just a little higher up.
That pesky greed thing is innate to human beings. Left to its own devices, it overrides any regard for the wellbeing of others.