I don't think it's about being ashamed - to me it is just sensible.
The problem that you have as soon as repro sticker is applied is that the ship can no longer be classified as a genuine vintage item. As the item is yours you can do what the hell you like with it, however the problem comes when you want to sell up or upgrade - you then need to inform the buyer exactly what he is getting and hope that he too is a stand up fella and will do the same when he moves it on
Also, God forbid something were to happen to you then if a family member or a friend tries to sell your stuff then they will not know what is vintage and what is not and will pass it on into the community.
For me there are 100's of decent vehicles and ships out there. If you aren't happy with the one you have then upgrade - generally if you sell your one and buy a better one then the difference in cost is not huge