It would warn users that these apps would be more likely to delete crucially important registry files by accident to clean up ...

Some Registry clean-up utilities also include defragmentation ... (Be warned: the old, free, unsupported RegClean utility from Microsoft doesn't really work for Windows XP, either).

This junk slows down the system and takes up ... free Registry Cleaners, Junk Cleaners, and Windows Optimizers. Mahit Huilgol is a Windows enthusiast, a blogger & a keen follower of everything ...