Many prominent church figures chose to live poor, mainly if they were monks and nuns. St. Anthony of Egypt sold his possessions and lived a very austere life. St. Mary of Egypt was the same. In fact, poverty is one of the pillars of monasticism. In choosing poverty, they wanted to separate themselves from earthly possessions and master themselves. History tells us this practice existed before Christianity, and many decided to live poor, e.g. stoics. In Christianity, those who chose to live poor do so to imitate Jesus, let go of any earthly attachment and be utterly dependent on God.
Gambero, L., 1999. Mary and the Fathers of the Church 1st ed. Translated by Buffer, T., San Francisco: Ignatius Press.