According to Revo Uninstaller, Blender adds more than 4400 registry keys to the Windows Registry. They are almost all spread in Registry folder:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\[your user string]\Components
Assuming that the Windows Registry is kind of a highway (database) where system and user applications will eventually want to quickly store and share data, unnecessarily growing it will impact other applications performance on accessing, not to mention the impact on registry backups that Windows makes periodically.
Next follows an old opinion of Jeff Atwood about using registry as a storage room (source: here):
a trash heap of miscellaneous junk settings for every rinky-dink application on the planet
Many of the 4400+ entries that Blender stores in Registry, if not all, are references to Python scripts, that I strongly doubt they really need to be stored in a system wide database, instead of a local configuration folder.