[Bruce Wayne]

here in the UK i do it because of what are called 'ringer' cars. With a reg plate splattered all over the interweb, it prevents some a-hole putting your reg on a stolen car. they can even get your vin number from the reg plate and put that on stolen car.

it does happen and often.

Mastermind of £1.2m car ringing scam jailed - Telegraph

In the dock with Khan, 31, of Osborne Road, Hornchuch, Essex, was Paul Pepper, 30, of Lathom Road, East Ham, east London, who received a 15 month sentence, and Michael Kellman, 40, of Romford Road, Forest Gate, east London, who received a two year sentence.

Also before the court were Sonny Sian, 22, of Woodgrange Court, Forest Gate, and Wayne Francis, 25, of Lindfield Road, Romford, Essex. They were each jailed for 36 weeks suspended for two years and subjected to supervision orders for the same period.
They variously admitted conspiracy to defraud, converting and concealing the proceeds of crime, theft, handling, and obtaining property by deception between January 2004 and December 2007.

Khan, who drove a £40,000 black Porsche [Cayenne] stolen for him, also pleaded guilty to fraud and obtaining a money transfer by deception.