People suffer to cleanse them of their sins. They have sinned because
they broke Hashem’s laws which Hashem put out in the beginning.
Children suffer, too. (So you’ll answer that they
must be a gilgul, but how do you know that?)
And we certainly see people who appear to us to have sinned
more seemingly suffering less than people who appear to have
sinned less do. It’s a hard answer for some people to accept.