A common response is "Capitalism". It's an easy, glib response. Unfortunately, it's not a good one, because abject poverty predates capitalism and exists without it.
Another response is "deprivation". Unfortunately, this response is effectively an appeal to the definition of poverty.
Since you asked what I believe, I don't believe there is a well-defined single cause of poverty.
A common response is "Capitalism". It's an easy, glib response. Unfortunately, it's not a good one
If anything, Capitalism has lifted 90% of the world's population out of poverty. It's a solution to absolute poverty, not a cause. It may, however, be a cause of relative poverty. But to paraphrase Winston Churchill, it's the worst system for eliminating poverty, after all the other ones we've ever tried.
Another response is "deprivation". Unfortunately, this response is effectively an appeal to the definition of poverty.
Since you asked what I believe, I don't believe there is a well-defined single cause of poverty.