Stops ppl nicking the car when its in there. ive seen ppl put chains across as well.
PPL get bitchy if people park in front of a drive way or in there normal spot on the road. if u just parked ur car in some ones drive u would probably come back to it just pushed in to the road or damaged in some way if u did it more than once.
Ive never seen any one do it or herd of some on have a stranger park in there drive way. and trust me its something people would bleat on about if it happened.
Fair enough parking is a problem, and ive seen ppl park in some strange places but no one parks in other peoples drive ways.
John