Or is it just that VW's have locks made of butter and high prices mean that there are lots of individuals prepared to take a risk....
Seriously. Aircooled VW locks are useless, i once lost my Fastback key so used my 1303 key for two months until it turned up. Even newer ones aren't much better, my friends's mk2 polo key opened (but wouldn't start) my G40. And even if you can't find a key to fit, the design of the door handles is terrible and if you don't mind puncturing the door skin, a swift blow from a flathead screwdriver gets you in.
People want something, they take it. Welcome to modern life and no amount of locks/alarms/taking parts off the engine will stop them.
Never trust a man Who names himself Trevor. Or one day you might find He's not a real drug dealer.