With moder Windows version, the real problem is not the registry, but the amount of small, random reads issued to the hard disk drive.
Yup. And the above mentioned crapware is a major contributor to this, especially during system startup and login. Modern OSes do try to minimize the amount of disk thrashing during startup, but they don't control what 3rd party applications do.
If the world isn't making sense to you, you're either drinking too much or not drinking enough.