Possibly there's some confusion here between 'register' and 'registry'?
The Mac operating system is Unix-based and, in common with all Unix systems, does not have a registry (which makes it far more robust than Windows).
The Windows registry seeks to draw together common elements of various programs. However, by linking programs together, it offers the possibility of producing system conflicts. The registry served a purpose when computer memory was limited and expensive. However, if Microsoft's programmers could start today with a 'blank sheet' it's extremely unlikely that they'd adopt the same concept. Unfortunately, unless they're prepared to produce a new operating system which is totally incompatible with all existing PC software, they're stuck with it.
Chris