1. Giving all to the poor may deprive our abilities to perform charity. Some saints have different takes on this, St. Anthony the Great was convincing himself that it is better to lose the opportunity to love rather than looking back and not deem worthy of being Jesus' disciple. St. Francis was focusing on voluntary holy poverty but does not remove himself from charitable work and does not reject the land of La Verna as donation.
2. Voluntary poverty forces us to remove all conveniences yet we still need to figure out how to stay alive. In case of St Francis who succeeded not enjoying donation for easy life like Francis seem to challenge God's providence daily without saving of what was already given by providence to remove one's dependency of material things. For some, leaving everything behind seem to be an act of leaving behind once, but still attain security through life of the Church in their future ministry.
This raises question what Jesus really suggested in perfection, it seems to us that He Himself never deprived Himself of food like Francis. One thing that is clear, when you give away everything without any sustanance, you are challenged by your own self who prevent you to move forward, and Jesus mentioned how we cannot enter the kingdom unless we are like children. It shows us that giving up all our possession seems to reveal plenty of our false securities and unhealthy mindsets, which we can remove to achieve child-likeness. Where the follow up perspective how to deal with those material if they come back are as the result of cleaned up mindsets of giving them all up.