At least Windows, having gone through this particular growing pain, is nowadays fairly painless to reinstall. Did OSX ever improve that aspect of their product?
2) The OS reinstall path is identical to the OS upgrade path, making it very well tested. This has been the case since (IIRC) Snow Leopard.
3) The latest few generations of hardware can even (re)install the OS over the internet, meaning you don't even need to carry around media to reinstall. (Assuming you're on a fast connection or are willing to wait.)
It's entirely painless to reinstall OS X.
If you want to replace various bits of the system, reinstall the OS.
These are different scenarios with different use-cases, and I'd argue it's a much worse idea to conflate the behaviours, as in certain other OSes, than OS X's fault for properly treating them as separate operations.
It's a good thing.