I googled the title of this one finding out that this actually came from a mother's saying. "That's why we can't have nice things," is very striking to me in a way it's very realistic and at the same time, tragic.
Try looking at your life there and back, how many times did you actually experience the "nice" things? All of this time, we are just working, studying or fighting life just to find contentment and happiness. To get that nicest thing perhaps is our ultimate goal.
And that is the reality. The tragedy of it is, we cannot hold that nicest thing and there will be always a nicer one to beat it. An endless ladder of contentment it is.
Happiness is like sadness. It will make you go to circles, make you chase forever and farther. You will get once, maybe twice or thrice but it will never stay in the palms of your hands like an object. And the worst part of it, once you get it, you will always try to get it again.
So that's why we cannot have nice things. How ironic, eh?