But why it is better if the same resource could be used to make something good - e.g. build a hospital for the poor or feed some starving people, etc.?
Putting that person further away from the police probably improves things, as I said, but better that we just build such hospitals and fund such social programs as we actually need, and not rely on people doing bad things (either the people whose stuff is being confiscated, or the police confiscating property of innocents) to make it happen.
Note again that at this scale cash isn't really a resource - it's a claim on resources. Destroying it doesn't destroy those resources, it releases the claim which winds up sort of distributed over other dollars.