I think it's much more to do with lower expectations.
Also you do find that people who own dacia's, Kia's etc kind of feel they have a point to prove and have to justify their decision so are always keen to support that choice. Not saying there is anything wrong with them by the way. We merc owners can't be bothered generally and except them to be faultless so when they do go wrong we moan!!!
I don't think these satisfaction surveys give an accurate picture.