I've seen small / light aluminium and copper stolen before in similar small weight quantities before, to a heroin addict its worth it, I've seen them cut every copper gas pipe to every house on a whole terraced street where the pipe comes out of the tarmac and elbows off in to the house, a foot of pipe per house!60p / Kg for clean aluminum scrap, is it worth the risk and hassle of removing a tyre? Maybe selling to a dodgy breaker or possible stealing to order.
If they are indeed stealing to order they'd have to target the right van for the specific wheel, which was my point.