Cos they are scrotes mate. I had a sign written van nicked back in 1999, had just picked it up from the garage 2 days previous, full of buckets and ladders, never seen it since, got the insurance then the police gave me a crime number and said that the engine and wheels would possibly shipped to Pakistan and that they usually crush the body at a scrapyard!
Not that i am bitter after all these years

Rant over