Because it’s easier to make money when you steal and have no costs than it is to build an orchard and work it.
Do you think the Mafia was just like “we’ll stop doing crime when we’re not poor anymore?”
If I leave a $50 bill on the table at a cafe or the library and go to the bathroom it’s not going to be there when I get back, someone will have taken it. It’s not because they were poor, it’s because someone could do so without consequences.