Why Does Evil Exist?

As a catholic I have always been asked this question but I never have put my thoughts into it. I know there is good and I know there is evil but why does the evil have to be present? Why can’t there just be good? Sadly, there is so much evil in this world. People killing others, stealing, lying, and doing other horrible things to one another. Could evil be around to balance the good? I am not sure but I think evil exist simply because there is so many things in this world that will kill the human soul and therefore make them evil once they lose their soul. There are so many vices in this world and people do them willingly because they want that short term good feeling coming into their body. This is not worth it because it is not going to be a good feeling that last forever. People should strive to be good but being good can be hard for many. Being evil takes no work or effort and I think thats why there is so much evil that is present currently and will be in the future.