The people living in poverty line aren't supposed to exist, the role that they play in the economy is that they are an indicator that there's inefficiency and incompetence when it comes to how the people that's in power run a country's economy. Poverty isn't something that any person should experience even if they are the lowest of the low in a society, anyone should have the access to basic needs like food and shelter. Making sure that everyone has a fair headstart makes for a competitive society that strives for greatness.