If God's all good and all loving, why wouldn't He prevent suffering? Man suffers physical evils from natural disasters like tornadoes to bodily ailments like cancer. He also suffers moral evils from attacks by his fellow man to personal sins that harm his soul. His sins can even cause eternal suffering in Hell.
Evil isn't a thing that's created: it's actually a lack of goodness. God only created good, as Genesis 1:31 attests: "God saw all the things that he had made, and they were very good."
Physical evils like natural disasters and illness are really a lack of the original harmony in nature. Moral evil, or sin, is simply a lack of moral rectitude in man's original relationship with God.
All physical and moral evil can be traced back to the fall of the angels and of man. Regarding the angelic rebellion, Wisdom 2:23–24 reads, "For God created man incorruptible. … But by the envy of the devil, death came into the world." Regarding the rebellion of Adam, St. Paul, in Romans 5:12, writes, "Wherefore as by one man, sin entered into this world, and by sin death; and so death passed upon all men."
The sin of Adam even affected all creation as Genesis 3:17–19 relates: "[C]ursed is the earth in your work; with labor and toil shall you eat thereof … till you return to the earth."
God created angels and men with free wills to love Him. If God prevents them from choosing evil, then they're not free to love. The good news is that God allows evil in order to bring forth a higher good. This is reaffirmed in paragraph 312 of the Catechism of the Catholic Church: "From the greatest moral evil ever committed — the rejection and murder of God's only Son, caused by the sins of all men — God, by his grace … brought the greatest of goods: the glorification of Christ and our redemption."
Learn the value of freedom from Dr. Charles Rice in season one of Church Militant's Premium show Right Reason—Freedom!