some fare points there.. but i also think it boils down to how a car has been engineered.. i think from what i have seen so far Japanese cars like Lexus, Toyota and Honda tends to have major engine and gearbox and exhaust parts designed to last at least 100 k miles.
all my cars have been 2nd hand the the only time i suffered an unexpected break down was in my Ford Cougar V6's alternator and Rover 45 head gasket but was still driveable which were both understood to be a design problem for those manufactures bedsides that i tend to do the preventative parts change every time i get a car like spark plugs auto gearbox oil change, cam belt change if its belt driven, basically anything related to oil or cooling i change them and by following this principal has mainly not left me stranded 9 out of 10 times in a second hand car. 'touch wood'
That's not saying 2nd hand Lemons don't exist but there are some decent cars with 50-100k miles on them that will do another 100K without encountering an unexpected break down and will still have performance and drive like it just rolled off factory if of course taken care of which wont cost an arm and leg either to maintain.