You are missing the point. It just gives you a better chance to find a car thats been owned by somebody for whom money wasn't an object, thats all. You might miss out on those cars where money wasn't an object and the owner was simply principled, but you'll also miss out on those cars where mony was an object and it got the cheapest deal each time.
Most people you'll buy this sort of car from are probably not enthusiasts. They don't make enthusiast based decisions - where to service will almost always come down to cost as the general public do beleive, rightly or wrongly, that main dealer = best.
Main dealer servicing isn't even that more expensive than an independant - I paid 30 quid more than the local indy for my Inspection 2. The experience was also much nicer. I parked up, walked inside the nice clean showroom, had a quick coffee whilst the paperwork was sorted out and then carried onto work in a brand new 120d. This beats going to the local indy, standing about in a small office on an industrial estate, and then either leaving on the bus, or if they've got a car, in a 14 year old 318i.
It's just nicer. And its hardly any more expensive. And it does your resale better (Though probably not in my case

).
Sure there is every chance somebody might mess something up but to be fair that chance exists equally if not more so at an 'indy'. There are one or two absolutely exceptional independants around but if you cant find that needle in the haystick or don't live near one you are at the mercy of the plethora of ordinary garages who decided to stick 'BMW and Audi and VAG' specialist above the door.
I do use a local independant for my repair work - and he's great - but this is because getting repairs done at BMW involves a random number generator whereas servicing is a fixed price entity. But the experience of using the indy isn't the same as that with using BMW, he never has a loan car available, etc etc. I'm happy to make that compromise for repair work because the saving to me is credible (ie not 50 quid here and there) but if I am buying a 3-4 year old BMW I want to buy it off somebody considerably more wealthy than myself and for whom that just isn't a consideration.
Doubtless further point-missing will now take place as you all describe in vivid detail the billionare who treats his 650i like a pile of crap and the unemployed guy who has the mintest M3 ever, but there we go
