That explains it all then
i guess cars today don't have to be painted everywhere ie boot, as in past years were cars used to rot manufactures would just coat them in anything they could.
good point... I know it annoys some people, but why would you want paint where no one sees it anyway 
less paint = less weight 
Because unlike a lot of people on here i keep cars for a long time. If the underside or panel edges are only primed and not undersealed or even top coat painted you get rust issues with time. Thats fine and not a problem when you only have the car 1,2 maybe 3 years but further down the line at 4 or 5 years old you get rusted through panels like the mk5's thats not good and they have cut back further with the 6 than the 5.
Plus some of the places mine isnt painted can be seen. If the suns shinning on the side of the car you can see the unpainted bit on the door jam from the other side of the car park (people at work have seen it and i have not said about it to them) as well as the gray bits in the A-pillar on the edges of the wings.
If im truthful with myself i should get rid and just run one of the other cars i own. But the hassle i went though to get the damb thing and i like the look of my Mk6 GTI, it makes me smile when i see it, its nice to drive and i like GTI's, the GTI name is probably the main reason i have not got rid, silly history from owning my mk1 for 22 years i guess. Silly really but its a hart over head thing but its not far off me making the decision and just keeping the leon instead or getting something else, do have a soft spot for a sepang blue TTRS at times.