Because if you don't do anything, the thief will have their actions validated. That theft will no longer be an isolated, one time occurrence... It will be their

Because if you don't do anything, the thief will have their actions validated. That theft will no longer be an isolated, one time occurrence... It will be their new full time job. That means that they are much more likely to end up robbing someone again, be it you, a close relative, a loved one, a person who can't afford to "move on with their life", as you said. I'm trying very hard not to use the word "sheeple" here, but you haven't left me many options. If the average person protects themselves, then the group or community, on average, will be protected.