I dunno why, but I have noticed and commented several times about how VW main dealers have second hand (probably dealer demo/company cars 6 months old) at prices which are mental compared to buying a new one at a discounted price.
I even had that conversation with my local dealer a few months back.
I think essentially nobody buys them and the idea is that nobody buys them at that price, they just exist to get people to buy a new one - a new one is another registration (that they need for their sales quota with VW) and a chance to get someone to take out a VW finance deal (which is probably also a sales target and certainly a cash payment from VW Finance)
It can't be for any other reason can it?