Reminds me of the issue with car tyres - I know it's far from a direct comparison but you'd assume car companies would usually specify the best tyres for the job, but they don't. They have alliances with manufacturers and doubtless it makes economic sense (obviously no parallel in that there's no freebie wire manufacturer making a profit in cahoots). Now all tyres 'work', but the difference between good and bad is significant - there are many group tests undertaken each year. I have a friend whose car is like mine in many respects (4wd, front-engine, powerful) and whilst mine is pretty much unaffected by rain/cold, his becomes a complete liability. This is not down to the car, it's down to the choice of tyres the manufacturer made.
exactly just like how some speaker (and amplifier) companies choose to use better quality cabling and some dont.
its similar to how you have discovered with your cd player that adding weight(s) and damping the components case work has brought sonic benefits where as yamaha and marantz, for example, already look into this aspect and include these features in their designs.
(my old sony cdp xb930e uk tuned was like a brick !)
overall it just depends on what areas a manufacturer decides to spend the budget on when designing kit at the end of the day.
all areas can effect the sound of a component in varying different levels.
just take a look at what goes into the design of "cost no object" hifi kit if you want to judge the effects of whether internal wire quality and damping components is a myth.
(cad / computer audio design and msb are 2 other ultra high end companies that i have contacted and have confirmed this to me to...)