One reason is because the burden to manufacture crimes is far higher. Every violent crime necessarily has a victim and if the victim survived the encounter they can identify affirmatively the characteristics of their assailant.

The problem with non-violent crimes is that they could be tainted by biases since there isn't always as concrete/reliable an eyewitness.

Someone attacks me and it's a lot easier to trust what I report. I see someone steal something at a distance, and my eyewitness account is less trustworthy.