I grumped about this a few years ago - I have done a search for it, but cannot find it. I presume it was a casualty of "The great GOM IT disaster" a few years ago.
http://news.bbc.co.uk/1/hi/uk/8118083.stm"The charity Keep Britain Tidy called on people to collect up bands dropped by postal workers after a survey claimed they were found on 6% of UK streets."
The article goes on to say that postpersons could face on the spot fines for littering. Why only "could"? If rubber bands are found on a certain street, surely they can trace the postperson responsible for that patch?
Get it sorted, postman prat.
Bastards.