It didn't have a full VW service history when I bought it and I'm one of those who couldn't care less where it was serviced as long as it's serviced on time and the receipts are there to prove what was done.
In my limited experience (and this only involves part-ex trade-ins) the question has always been has it got a full service history, they haven't cared if it was full dealer or not and it didn't increase their offer on trade-in. If private buyers care then they won't buy my car when I sell it, that's their choice but I really don't think it's an issue nowadays.