I guess that this is inevitable given that, as you say, all the cars are loaned by generally careful and proud owners.
To see cars as they were, the only way is to view old films such as those mentioned in previous posts. Watching 'Gumshoe' (released 1971) last night with Albert Finney and Billie Whitelaw in a Lotus Europa brought home this point. Although much later than some of the periods featured in recent productions, most of the cars featured looked well worn and less than pristine. Having said that, most of the buildings and street scenes looked pretty grubby too. We have probably forgotten that even within our driving lifetimes (well, some of us at least) most aspects of our environment have changed visually. It was not until the 80s that city buildings started to be refurbished en masse and their thick coating of velvety soot cleaned off. Gumshoe was a colour film but it may well have been in black and white!
