Because insurance premiums are based on statistics (and I would imagine nowadays a real person doesn't get involved in the calculations).Why tho? That was a one-off event. It doesn't mean that the risk in that area is any higher than any other area. The chance of this happening again in the same place would be incredibly slim, and it doesn't indicate an ongoing risk in that area.
It's not like areas where theft is higher, or some other tangible on-going risk is greater. This is a one-off, unfortunate accident. Why would that push premiums in that area up? Don't understand.